Entertainment a cop pays for (5)
I believe the answer is:
funds
'pays for' is the definition.
('fund' can be a synonym of 'pay for')
'entertainment a cop' is the wordplay.
'entertainment' becomes 'fun' (fun is something entertaining).
'a cop' becomes 'ds' (Detective Sergeant).
'fun'+'ds'='FUNDS'
(Other definitions for funds that I've seen before include "Available cash" , "Finances" , "Liquid assets" .)