Very large seabird (9)
I believe the answer is:
albatross
'very large seabird' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for albatross that I've seen before include "Ocean bird; a burden (round neck)" , "Ancient Mariner bird" , "Sea bird" , "something few golfers achieve" , "Atlas bros alter the large bird with narrow wings" .)