Nag about wife getting bite (4)
I believe the answer is:
gnaw
'bite' is the definition.
(gnawing is a kind of biting)
'nag about wife getting' is the wordplay.
'about' indicates anagramming the letters.
'wife' becomes 'w' (abbreviation).
'getting' means one lot of letters go next to another.
'nag' anagrammed gives 'gna'.
'gna'+'w'='GNAW'
(Other definitions for gnaw that I've seen before include "Bite and wear away" , "Chew steadily at" , "Bite persistently, grind" , "Wear away with the teeth" , "Nibble like a rodent" .)