Gambler leaving with more money (6,3)
I believe the answer is:
better off
'with more money' is the definition.
(I've seen this before)
'gambler leaving' is the wordplay.
'gambler' becomes 'better' (someone who makes bets is a gambler).
'leaving' becomes 'off' (as in 'I'm off').
'better'+'off'='BETTER-OFF'
(Other definitions for better off that I've seen before include "in happier financial circumstances" , "wealthy" , "Someone setting out for the bookies" , "with more money" , "having lost less" .)