Bird on board (4)
I believe the answer is:
rook
This might be a double definition.
'bird' is the first definition.
(rook is a kind of bird)
'board' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'on' is the link.
Can you help me to learn more?
(Other definitions for rook that I've seen before include "Chesspiece otherwise known as a castle" , "Castle -- bird" , "Man in game" , "Gregarious black bird" , "Rank - and - file man" .)