Rapacious seabird (4)
I believe the answer is:
skua
'rapacious seabird' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for skua that I've seen before include "Predatory northern seabird" , "Flyer" , "Large brown seabird" , "Large sea bird" , "Auks (anag.)" .)