Scratching an ace copper plate finish (9)
I believe the answer is:
culminate
'finish' is the definition.
(I know that culminate is a type of finish)
'scratching an ace copper plate' is the wordplay.
I cannot really see how this works, but
'an' could be 'i' (Roman numeral for one) and 'i' is found in the answer.
'ace' could be 'a' and 'a' is found in the answer.
'copper' could be 'cu' (chemical symbol) and 'cu' is located in the answer.
'plate' could be 'l' (from the L-plate that Learner drivers use) and 'l' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for culminate that I've seen before include "Bring to high point" , "End" , "Wind up" , "Reach a climax" , "Come to a climax (in)" .)