Exhausts betting and finishes (6)
I believe the answer is:
spends
'exhausts' is the definition.
(I've seen this in another clue)
'betting and finishes' is the wordplay.
'betting' becomes 'sp'.
'and' is a charade indicator (letters next to each other).
'finishes' becomes 'ends' ('end' can be a synonym of 'finish').
'sp'+'ends'='SPENDS'
(Other definitions for spends that I've seen before include "Gives money to pay for goods" , "Pays money or passes time" , "Disburses, does not save" , "Lays out (money)" , "drains" .)