Cheat man on board (4)
I believe the answer is:
rook
I believe this is a double definition.
'cheat' is the first definition.
(I know that rook is a kind of cheat)
'man on board' is the second definition.
(man can mean a chess piece)
(Other definitions for rook that I've seen before include "Gregarious crow" , "Use deceit to get money" , "Gregarious black bird" , "Crow-like bird" , "Steal - castle" .)