Fine avoided by prosperous drunkard (4)
I believe the answer is:
lush
'drunkard' is the definition.
(I know that lush is a type of drunkard)
'fine avoided by prosperous' is the wordplay.
'fine' becomes 'f' (abbreviation).
'avoided by' suggests deleting specific letters.
'prosperous' becomes 'flush' (flush can mean financially prosperous).
'flush' with 'f' taken out is 'LUSH'.
(Other definitions for lush that I've seen before include "Habitual drinker (slang)" , "Abounding in lavish growth - alcoholic" , "Verdant" , "Growing thickly; drunkard" , "Succulent - heavy drinker" .)