Stooge is a man on board (4)
I believe the answer is:
pawn
I believe this clue is a double definition.
'stooge' is the first definition.
(I've seen this in another clue)
'a man on board' is the second definition.
(chess)
'is' is the link.
(Other definitions for pawn that I've seen before include "one used by another" , "Chess piece -- puppet" , "One getting used" , "Minor chess piece" , "making deposit for a loan" .)