Tengo que pasarle la plancha a esta camisa antes de salir.

It means to iron something, literally to pass the iron over it.

In this sentence:

• la plancha = the iron
• pasar = to pass / move over
• pasarle la plancha a esta camisa = to run the iron over this shirt

So although the literal structure is different from English, the natural meaning is simply to iron this shirt.

Le refers to esta camisa.

The structure is:

• pasar la plancha a algo = to pass the iron over something
• le = to it
• a esta camisa = to this shirt

So pasarle la plancha a esta camisa is, very literally, something like:

to pass the iron to/over this shirt

In natural English, of course, we just say to iron this shirt.

Because le is an indirect object pronoun, and indirect object pronouns do not show gender in the singular.

So:

• le = to him / to her / to it / to you (formal)

Here it refers to la camisa, but it stays le, not la.

By contrast:

• la would be a direct object pronoun, as in La plancho = I iron it.

So the sentence uses le because camisa is functioning as the indirect object in this expression.

Because esta camisa is introduced as the indirect object:

• pasarle la plancha a esta camisa

That a is not the personal a. It is there because the verb pattern here includes an indirect object:

• pasar algo a alguien / a algo

In this sentence:

• la plancha = direct object
• a esta camisa = indirect object

So the a is part of the normal grammar of the construction.

Yes — and in many situations that is the simpler and more common way to say it.

• Tengo que planchar esta camisa. = I have to iron this shirt.

Compared with that:

• Tengo que pasarle la plancha a esta camisa.

sounds a bit more descriptive, literally focusing on passing the iron over the shirt.

Both are correct, but planchar is usually the more straightforward everyday choice for learners.

Tengo que + infinitive is a very common way to say I have to ...

So:

• Tengo que pasarle la plancha... = I have to iron...

It expresses obligation or necessity.

You could also hear:

• Debo planchar esta camisa = I should / I must iron this shirt

But tengo que is often the most natural everyday equivalent of have to.

It means before leaving or before going out.

Breakdown:

• antes de = before
• salir = to leave / to go out

So:

• antes de salir = before leaving / before going out

In context, it probably means the speaker needs to iron the shirt before leaving the house or before going out somewhere.

Because after antes de, Spanish normally uses the infinitive when the subject is the same as in the main clause.

Here the subject of both actions is I:

• Tengo que... = I have to...
• salir = leave / go out

So Spanish uses:

• antes de salir = before leaving

If the subject were different, the structure would change, for example:

• antes de que él salga = before he leaves

It could mean either, depending on context.

In this sentence, both are possible:

• before leaving
• before going out

If the speaker is getting ready to go somewhere socially, go out may fit well. If the focus is simply on leaving the house, leave may be better.

Spanish salir often covers both ideas.

It is understandable and natural, but many speakers would probably more often say:

• Tengo que planchar esta camisa antes de salir.

The version with pasarle la plancha is a bit more literal and expressive, as if you are picturing the action of using the iron.

So for a learner:

• planchar = the safest, simplest verb to use
• pasarle la plancha a ... = also correct and useful to recognize

Esta means this and agrees with camisa:

• camisa is feminine singular
• so the demonstrative is esta

That gives:

• esta camisa = this shirt

If it were masculine, you would use este:

• este libro = this book

You can, but it sounds unnatural in English.

A very literal version would be something like:

• I have to pass the iron over this shirt before going out.

That helps show the grammar, but the natural English translation is:

• I have to iron this shirt before leaving.

So the literal meaning is useful for understanding the Spanish structure, even though it is not the best final translation.

In practice, le is very natural in this sentence and helps Spanish sound complete and idiomatic.

So:

• Tengo que pasarle la plancha a esta camisa sounds very natural.

Without le, some speakers may still understand it, but the version with le is the one learners should expect and probably use with this kind of pattern.

So the safest answer is: keep the le.