Very distressed copper knocked back plonk (3,2)
I believe the answer is:
cut up
'very distressed' is the definition.
(I've seen this before)
'copper knocked back plonk' is the wordplay.
I cannot quite understand how this works, but
'copper' could be 'cu' (chemical symbol) and 'cu' is found within the answer.
The remaining letters 'tup' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for cut up that I've seen before include "Distressed - dissected" , "Extremely upset" , "Dissect" , "Sliced; distressed" , "Very unhappy" .)