Women in very French trousers (5)
I believe the answer is:
trews
'trousers' is the definition.
(trews is a kind of trousers)
'women in very french' is the wordplay.
'women' becomes 'w' (standard abbreviation).
'in' is an insertion indicator.
'very french' becomes 'tres' ('very' in French).
'w' placed within 'tres' is 'TREWS'.
(Other definitions for trews that I've seen before include "Wrest (anag) - trousers" , "Garment" , "close-fitting garments" , "Trousers of a Scot" , "Item of clothing" .)