Colour of carbon paper (5)
I believe the answer is:
cream
'colour of' is the definition.
The definition and answer can be both groups as well as being singular nouns.
Maybe there's an association between them I don't understand?
'carbon paper' is the wordplay.
'carbon' becomes 'C' (chemical symbol).
'paper' becomes 'ream' (a ream is an amount of paper).
'c'+'ream'='CREAM'
Can you help me to learn more?
(Other definitions for cream that I've seen before include "Thick milk" , "Butterfat part of milk" , "Dairy product" , "treat for cat?" , "It rises to the top, the best" .)