Gambler not doing well with additional funds? (6,3)
I believe the answer is:
better off
'with additional funds?' is the definition.
(better off can mean with more money)
'gambler not doing well' is the wordplay.
'gambler' becomes 'better' (someone who makes bets is a gambler).
'not doing well' becomes 'off' ('off' can mean feeling unwell).
'better'+'off'='BETTER-OFF'
(Other definitions for better off that I've seen before include "Richer" , "having lost less" , "with more money" , "wealthy" , "in happier financial circumstances" .)