Very large seabird (9)
I believe the answer is:
albatross
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">very large seabird</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(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" .)