Black stick used for drawing (8)
I believe the answer is:
'black stick used for drawing' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for charcoal that I've seen before include "Black carbon produced by burning wood" , "Fuel - very dark grey" , "Black stuff for burning or drawing" , "Form of carbon for drawing" , "Stick of black carbon material used for drawing" .)