Long-gone bird (4)
I believe the answer is:
dodo
'long-gone bird' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for dodo that I've seen before include "Large extinct bird" , "Bird (whose style of very out of fashion)" , "Old-fashioned person" , "Extinct bird of Mauritius, very dead" , "Mauritian bird no more" .)