Support for coppers (4)
I believe the answer is:
prop
'support' is the definition.
(prop up can mean to support)
'for coppers' is the wordplay.
'for' becomes 'pro' (as in being 'pro' something).
'coppers' becomes 'p'.
'pro'+'p'='PROP'
(Other definitions for prop that I've seen before include "Support to keep from falling" , "Lean" , "What actor may carry" , "player involved in scrum" , "Stay" .)