Dominant leg-spinner (2,3)
I believe the answer is:
on top
'dominant' is the definition.
(on top can mean dominant or in the ascendancy)
'leg-spinner' is the wordplay.
'leg' becomes 'on' (cricket term, fielding positions).
'spinner' becomes 'top' (a spinning top).
'on'+'top'='ON TOP'
(Other definitions for on top that I've seen before include "In a dominant position" , "Leading" , "At the summit or in superior position" , "Winning" .)