Garment very French worn by women (5)
I believe the answer is:
trews
'garment' is the definition.
(trews is a kind of garment)
'very french worn by women' is the wordplay.
'very french' becomes 'tres' ('very' translated into French).
'worn by' means one lot of letters goes inside another (I've seen this in other clues).
'women' becomes 'w'.
'tres' enclosing 'w' is 'TREWS'.
(Other definitions for trews that I've seen before include "Garment" , "nether garments" , "Trousers of a Scot" , "close-fitting garments" , "Wrest (anag) - trousers" .)