At a clothes' shop

At a clothes' shop
 

Is this Ok? Or should it be at a clothes shop without the apostrophe?

I would not put an apostrophe. Clothes as a plural noun to me is used adjectivally, not as a genitive.

A sports club
An accountants department
A clothes shop

A friend who is a native Spanish speaker (and who is also fluent in English) had this conversation with me just the other day about "clothes and shoes" and why and when they're plural.

"Clothes" is always plural. Never with an apostrophe (unless, for some strange reason, it's possessive, but I can't think of a good case for that). If you want to talk about "one item of clothing", that works.

"Shoes" is often plural, but you can talk about "one shoe".

English is weird.

no apostrophe.

or you can say clothing store