Overcharge man on board (4)
I believe the answer is:
rook
I believe this clue is a double definition.
'overcharge' is the first definition.
(I've seen this before)
'man on board' is the second definition.
(chess)
(Other definitions for rook that I've seen before include "Rip off - bird" , "man for moving" , "16" , "Man in game" , "Chess piece or crow" .)