Bird man on board (4)
I believe the answer is:
rook
I believe this is a double definition.
'bird' is the first definition.
(rook is a kind of bird)
'man on board' is the second definition.
(chess)
(Other definitions for rook that I've seen before include "Rank - and - file man" , "Species of crow" , "Ringing in the ears" , "Another name for castle in chess" , "embattled man" .)