Wife in thong (4)
I believe the answer is:
whip
'thong' is the definition.
(thesaurus)
'wife in' is the wordplay.
'wife' becomes 'w'.
'in' becomes 'hip' (both can mean fashionable).
'w'+'hip'='WHIP'
(Other definitions for whip that I've seen before include "Political officer who ensures party members attend and vote" , "Riding crop" , "Parliamentary disciplinarian" , "Pudding" , "cat" .)