Coal product (4)
I believe the answer is:
coke
'coal product' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for coke that I've seen before include "Substance left after gas and tar have been extracted from coal" , "Nose candy" , "Drug (abbr) - soft drink (abbr)" , "Carbon fuel" , "Carbonised fuel residue" .)