Large fish-eating bird of prey (6)
I believe the answer is:
osprey
'large fish-eating bird of prey' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for osprey that I've seen before include "Large bird that preys on fish in inland waters" , "Marine bird of prey" , "One flying" , "Bird from an outsize victim" , "Piscivorous creature" .)