La dueña del piso nos deja usar el aparador antiguo con tal de que lo limpiemos bien.

Because dueña is the feminine form of dueño. It means female owner or landlady, depending on context.

• el dueño = the male owner
• la dueña = the female owner

Here, the person who owns the flat is female, so Spanish uses la dueña.

Del is a contraction of de + el:

• de = of
• el piso = the flat/apartment

So la dueña del piso means the owner of the flat.

In Spain, piso very commonly means flat/apartment. In Latin American Spanish, apartamento or departamento may be more common depending on the country.

In Spain, piso usually means a flat or apartment in a building, while casa means a house.

So this sentence suggests they are talking about a flat, not a detached house.

• piso = flat/apartment
• casa = house

This is a useful Spain-specific vocabulary point.

This is the pattern dejar + infinitive, which means to let/allow someone to do something.

• deja = lets/allows
• nos = us
• usar = to use

So nos deja usar literally means she lets us use.

This structure is very common:

• Me deja entrar. = She lets me come in.
• No nos dejan fumar. = They don’t allow us to smoke.

Because nos is an unstressed object pronoun, and in normal finite verb structures it usually goes before the conjugated verb.

So:

• La dueña nos deja usar... = The owner lets us use...

With an infinitive construction, Spanish often has two possibilities in similar sentences:

• Nos deja usarlo
• Deja que lo usemos

But here, since deja is conjugated, nos naturally comes before it.

Aparador is a noun. In Spain, it usually refers to a piece of furniture like a sideboard, cabinet, or dresser, depending on context.

So el aparador antiguo is an old piece of furniture, not a verb or adjective.

This word can be tricky because it may not have one perfect English equivalent in every situation.

In Spanish, adjectives often come after the noun. So:

• el aparador antiguo = the old sideboard/cabinet

When an adjective comes after the noun, it is often more neutral and descriptive.

If you moved antiguo before the noun, el antiguo aparador, it could sound more like the former/old one in a more interpretive or stylistic way, depending on context. Here, after the noun is the normal choice for simply describing the furniture as old.

Con tal de que is a fixed expression meaning provided that, as long as, or on condition that.

It introduces a condition:

• She lets us use it, provided that...

The que is part of the expression and introduces the following clause.

Other similar expressions are:

• siempre que = as long as / provided that
• a condición de que = on condition that

Because con tal de que triggers the subjunctive. It introduces a condition, requirement, or something not yet realized, and Spanish normally uses the subjunctive after it.

So:

• con tal de que lo limpiemos bien

uses limpiemos, which is the present subjunctive of limpiar.

This is a very common pattern:

• Te ayudo con tal de que me escuches.
• Podéis salir con tal de que volváis pronto.

Limpiemos is the present subjunctive, first person plural (we form), of limpiar.

Compare:

• Indicative: limpiamos = we clean / we are cleaning
• Subjunctive: limpiemos = that we clean

The vowel change from -a- to -e- is typical for -ar verbs in the present subjunctive:

• limpie
• limpies
• limpie
• limpiemos
• limpiéis
• limpien

Lo is a direct object pronoun meaning it, and it refers back to el aparador antiguo.

So:

• el aparador = masculine singular noun
• therefore lo = it

That is why Spanish does not repeat the noun:

• ...con tal de que lo limpiemos bien
• literally: ...provided that we clean it well

Because aparador is the direct object of limpiar.

You clean something, so the thing being cleaned is a direct object:

• limpiar el aparador → limpiarlo / lo limpiemos

In standard Spanish:

• lo / la / los / las = direct object pronouns
• le / les = indirect object pronouns

So lo is the expected form here.

Bien means well/properly/thoroughly here. It adds the idea that simply cleaning it is not enough; it must be cleaned properly.

So there is a difference between:

• lo limpiemos = we clean it
• lo limpiemos bien = we clean it well / properly

It makes the condition stricter.

Not exactly in the same way.

• Con tal de que means provided that / as long as, and it strongly emphasizes a condition.
• Si simply means if and is more neutral.

So:

• La dueña del piso nos deja usar el aparador antiguo con tal de que lo limpiemos bien. = She lets us use it provided that we clean it well.

If you used si, the sentence would feel a bit different in tone and structure. Con tal de que is the more natural choice when someone sets a condition for permission.

Because usar is an infinitive, and after dejar Spanish normally uses a bare infinitive directly:

• dejar + infinitive
• deja usar = lets [someone] use

Spanish does not need anything like to before the infinitive in this structure, and it does not use an article here.

Compare:

• Nos deja entrar.
• Me dejan salir.
• Te deja cogerlo.

Yes, at least partly. The most obvious Spain-specific feature here is piso for flat/apartment.

The grammar itself—dejar + infinitive, con tal de que + subjunctive, lo limpiemos bien—is standard Spanish and would be understood everywhere.

So the sentence is not uniquely from Spain in grammar, but the vocabulary choice piso strongly fits Peninsular Spanish.