Boast about fight (4)
I believe the answer is:
crow
'boast' is the definition.
(crowing is a kind of boasting)
'about fight' is the wordplay.
'about' becomes 'c' (abbreviation for 'circa').
'fight' becomes 'row'.
'c'+'row'='CROW'
(Other definitions for crow that I've seen before include "Black bird with raucous call" , "Express triumph; bird" , "One commonly stoned" , "Gloat" , "Make sounds of pleasure as a baby does - or a bird" .)