More successful punter? (6)
I believe the answer is:
Here is my best explanation:
This clue might be a double definition.
'more' is the first definition.
'successful punter?' is the second definition.
'better' can be an answer for 'punter?' ('better' can be a synonym of 'punter'). I am not sure about the 'successful' bit.
(Other definitions for better that I've seen before include "Gambler; more effective", "Recovered; gambler", "More acceptable", "Reformed", "cap", "Speculator", "Superior; gambler", "One may lay", "Preferable" and "no longer sick".)