Market willing to identify legitimate target (4,4)
I believe the answer is:
fair game
'legitimate target' is the definition.
(I've seen this before)
'market willing' is the wordplay.
'market' becomes 'fair' (I've seen this in other clues).
'willing' becomes 'game' (I've seen this before).
'fair'+'game'='FAIR GAME'
'to identify' is the link.
(Other definitions for fair game that I've seen before include "Legitimate target for attack or exploitation" , "legitimate target for ridicule?" , "Acceptable target?" , "Legitimate objects for attack" , "Reasonable target?" .)