Witty remark, one for each copper
I believe the answer is:
apercu
'witty remark' is the definition.
(I've seen this before)
'one for each copper' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'for each' becomes 'per' (I've seen this before).
'copper' becomes 'Cu' (chemical symbol).
'a'+'per'+'cu'='APERCU'
(Other definitions for apercu that I've seen before include "Intuition" , "brief explanation" , "Precis, brief outline" , "what's observed" , "Illuminating comment or brief reference, to the French" .)