Alloy of copper makes money (5)
I believe the answer is:
brass
I believe this clue is a double definition.
'alloy of copper' is the first definition.
(I know that brass is a alloy of copper)
'money' is the second definition.
(informal term for money)
'makes' acts as a link.
(Other definitions for brass that I've seen before include "Alloy; effrontery" , "Metal alloy" , "Metal - cheek" , "Boldness" , "instrumental group" .)