Fashions that seem a bit nasty to the French? (6)
I believe the answer is:
styles
'fashions that seem' is the definition.
'styles' can be an answer for 'fashions' ('style' can be a synonym of 'fashion'). I am not certain of the rest of the definition.
'a bit nasty to the french?' is the wordplay.
'a bit nasty' becomes 'sty' (I can't explain this - if you can you should give a lot more credence to this answer).
'to the french?' becomes 'les' (plural form of 'the' in French).
'sty'+'les'='STYLES'
Can you help me to learn more?
(Other definitions for styles that I've seen before include "where there was a mysterious affair involving Poirot" , "Fashions and manners" , "Ways of writing, painting etc" , "Fashions and trends" , "'Fashions, modes (6)'" .)