Wife sears fresh fish (6)
I believe the answer is:
wrasse
'fish' is the definition.
(wrasse is a kind of fish)
'wife sears fresh' is the wordplay.
'wife' becomes 'w'.
'fresh' indicates anagramming the letters.
'sears' is an anagram of 'rasse'.
'w'+'rasse'='WRASSE'
(Other definitions for wrasse that I've seen before include "catch in the deep" , "Bright marine fish" , "Swimmer" , "Fish - swears (anag)" , "Type of fish" .)