Vicinus marito consilium tradit, ut officina melius custodiri possit.

Because marito is the indirect object of tradit.

The basic idea is:

• vicinus = the neighbor
• consilium = advice / a plan
• tradit = hands over, gives, delivers
• marito = to the husband

So the structure is:

The neighbor gives advice to the husband.

In Latin, the person to whom something is given is normally put in the dative.

Vicinus is nominative singular.

It is the subject because:

• it is in the nominative case
• tradit is 3rd person singular
• so vicinus tradit means the neighbor gives

A learner should also notice that vicinus is masculine in form. A feminine form would be vicina.

Literally, consilium tradit means something like:

• hands over advice
• passes on a plan
• gives advice

The noun consilium can mean advice, plan, decision, or strategy, depending on context.
The verb tradit often means hands over, delivers, passes on, or entrusts.

So in smooth English, consilium tradit is often best understood as gives advice or offers a plan.

Ut introduces a purpose clause.

So:

• ut officina melius custodiri possit

means

• so that the workshop can be guarded better
• or more literally, in order that the workshop may be able to be guarded better

This tells us the purpose of the neighbor’s advice.

A very common Latin pattern is:

• main verb + ut + subjunctive

when the subordinate clause expresses purpose.

Because after ut in a purpose clause, Latin normally uses the subjunctive.

So:

• potest = can, in a straightforward statement
• possit = may be able to / can, in a subjunctive clause of purpose

Here Latin is not simply stating a fact about the workshop. It is expressing the goal of the advice:

• the neighbor gives advice so that the workshop may be able to be guarded better

That is why possit is correct.

This is because of sequence of tenses.

The main verb is tradit, which is present tense.
After a present main verb, Latin usually uses the present subjunctive in a purpose clause.

So:

• tradit = present
• possit = present subjunctive

If the main verb were in a past tense, you would more likely expect posset.

Custodiri is the present passive infinitive of custodire, meaning to guard or to protect.

So:

• custodire = to guard
• custodiri = to be guarded

It is passive because the workshop is not doing the guarding. The workshop is the thing being guarded.

That is why the clause means:

• so that the workshop can be guarded better

not

• so that the workshop can guard better

This is a very common Latin construction:

• possum + infinitive = can / be able to + verb

Here the infinitive is passive:

• custodiri = to be guarded

So:

• officina custodiri possit

means

• the workshop can be guarded
• or more literally, the workshop may be able to be guarded

In natural English, we usually simplify it to can be guarded.

Officina is nominative singular.

It is the subject of possit and also the logical subject of the passive infinitive custodiri.

So the structure is:

• officina = the workshop
• custodiri possit = can be guarded

Together:

• the workshop can be guarded

Even though officina is in the subordinate clause, it is still nominative because it is the subject of that clause.

Because melius is an adverb, while melior is an adjective.

Here Latin wants to say guarded better, and better is modifying the verbal idea custodiri. That requires an adverb.

So:

• melior = better, as an adjective
• melius = better, as an adverb

Therefore:

• melius custodiri = to be guarded better

Tradit is present indicative active, 3rd person singular.

That means:

• he gives
• she gives
• the neighbor gives

In this sentence it presents the action as a simple present fact:

• The neighbor gives advice to the husband

Yes, the word order is fairly flexible.

Latin uses case endings much more than English, so the grammatical roles are clear even if the order changes.

This sentence is arranged in a fairly understandable way:

• Vicinus = subject first
• marito = indirect object
• consilium = direct object
• tradit = verb
• then the purpose clause

But Latin could rearrange the words for emphasis. For example, putting melius earlier might emphasize better, and putting officina earlier in the clause might emphasize the workshop.

So the exact order here is natural, but not the only possible one.

It could mean several related things, including:

• advice
• plan
• strategy
• decision

In this sentence, because the neighbor is giving something to the husband and it is followed by a purpose clause, advice or a plan both make sense.

A learner should remember that many Latin nouns have a wider range of meaning than any single English word. Context tells you which shade is best.