Charlie is playing Henry for money (4)
I believe the answer is:
cash
'for money' is the definition.
(cash is a type of money)
'charlie is playing henry' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'is playing' becomes 'as' (eg Ian McKellen 'as' Gandalf).
'henry' becomes 'H' (symbol for the unit of electrical inductance).
'c'+'as'+'h'='CASH'
(Other definitions for cash that I've seen before include "Money in the form of notes and coins" , "Till" , ""Readies"" , "Ready money" , "Funds" .)