Large diving seabird (9)
I believe the answer is:
cormorant
'large diving seabird' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cormorant that I've seen before include "High-flier" , "Proverbially gluttonous seabird" , "Black/white fish eater" , "Large fishing bird" , "Diver" .)