Man on board leading woman (5)
I believe the answer is:
queen
I believe this clue is a double definition.
'man on board' is the first definition.
(chess)
'leading woman' is the second definition.
(woman who rules)
(Other definitions for queen that I've seen before include "Empress" , "ER, say?" , "who collaborated musically with 14 [BOWIE]" , "Tom's partner" , "Female cat" .)