Yet she may be a man on board (5)
I believe the answer is:
queen
'man on board' is the definition.
(chess)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for queen that I've seen before include "Promote pawn" , "ER, say?" , "powerful man on board" , "Ruling lady" , "Female sovereign ruler" .)