Outdo punter (6)
I believe the answer is:
better
I believe this is a double definition.
'outdo' is the first definition.
(bettering is a kind of outdoing)
'punter' is the second definition.
(someone having a bet or punt)
(Other definitions for better that I've seen before include "punter" , "M ore appropriate" , "One may lay" , "'Discretion is the . . . . . . part of valour'" , "More appropriate; gambler" .)