A bird to fight and squabble (7)
I believe the answer is:
sparrow
'a bird' is the definition.
(sparrow is a kind of bird)
'fight and squabble' is the wordplay.
'fight' becomes 'spar' (sparring is a kind of fighting).
'and' is a charade indicator (letters next to each other).
'squabble' becomes 'row' (I've seen this in another clue).
'spar'+'row'='SPARROW'
'to' is the link.
(Other definitions for sparrow that I've seen before include "Bird with cockney associations" , "Pirate" , "(Formerly very) common British bird" , "Who killed Cock Robin" , "Robin's slayer" .)