Moneyed gentleman holding advantage (4)
I believe the answer is:
edge
'advantage' is the definition.
(I've seen this before)
'moneyed gentleman holding' is the wordplay.
'holding' indicates the answer is hidden within the clue.
'EDGE' can be found hidden inside 'moneyed gentleman'.
(Other definitions for edge that I've seen before include "Upper hand" , "Bite" , "'Margin, rim (4)'" , "Border, fringe" , "Move furtively; intense quality" .)