Pay out, betting on conclusion (5)
I believe the answer is:
spend
'pay out' is the definition.
(I've seen this in another clue)
'betting on conclusion' is the wordplay.
'betting' becomes 'sp'.
'on' means one lot of letters go next to another.
'conclusion' becomes 'end' (something's conclusion is its end).
'sp'+'end'='SPEND'
(Other definitions for spend that I've seen before include "Pay out (money)" , "Outlay" , "Pass time or pay out" , "Run through" , "Part with money" .)