Legitimate target in passable match (4,4)
I believe the answer is:
fair game
'legitimate target' is the definition.
(I've seen this in another clue)
'passable match' is the wordplay.
'passable' becomes 'fair' (synonyms).
'match' becomes 'game' (I've seen this before).
'fair'+'game'='FAIR GAME'
'in' acts as a link.
(Other definitions for fair game that I've seen before include "Legitimate target like blonde animal" , "legitimate target for ridicule?" , "Aunt Sally, for example" , "Acceptable target?" , "coconut shy?" .)