Copper to start with tasty prune (3)
I believe the answer is:
cut
'prune' is the definition.
(I know that prune can be written as cut)
'copper to start with tasty' is the wordplay.
'copper' becomes 'cu' (chemical symbol).
'to start with' indicates taking the first letters.
The first letter of 'tasty' is 't'.
'cu'+'t'='CUT'
(Other definitions for cut that I've seen before include "Discount" , "Truncate; slice" , "minor injury" , "Intersect; reduce" , "Stop filming" .)