Bird’s large victim (6)
I believe the answer is:
osprey
'bird's' is the definition.
(osprey is a kind of bird)
'large victim' is the wordplay.
'large' becomes 'os'.
'victim' becomes 'prey' (prey is a kind of victim).
'os'+'prey'='OSPREY'
(Other definitions for osprey that I've seen before include "Large bird that fishes inland waters" , "Spy roe (anag)" , "Fish-eater" , "Fish-eating raptor" , "Large fish-eating bird of prey" .)