Not much of a difference for coppers (5,6)
I believe the answer is:
small change
'coppers' is the definition.
(as in copper coins)
'not much of a difference' is the wordplay.
'not much of' becomes 'small' (I can't justify this - if you can you should believe this answer much more).
'a difference' becomes 'change' (change is a kind of difference).
'small'+'change'='SMALL CHANGE'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for small change that I've seen before include "Chickenfeed" , "minor reorganisation" , "hardly any difference!" , "Pennies" , "Not much difference" .)