Bird appearing in fight after fight (7)
I believe the answer is:
sparrow
'bird' is the definition.
(sparrow is a kind of bird)
'fight after fight' is the wordplay.
'fight' becomes 'spar' (sparring is a kind of fighting).
'after' means one lot of letters go next to another.
'fight' becomes 'row' (I've seen this in another clue).
'spar'+'row'='SPARROW'
'appearing in' acts as a link.
(Other definitions for sparrow that I've seen before include "a British resident" , "Small brown bird" , "Common town bird" , "Pirate" , "Little brown bird" .)