A cleaner fuel used by artists (8)
I believe the answer is:
charcoal
'used by artists' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives can sometimes mean the same thing.
'a cleaner fuel' is the wordplay.
'a cleaner' becomes 'char' (char can mean a cleaner).
'fuel' becomes 'coal' (coal is a kind of fuel).
'char'+'coal'='CHARCOAL'
Can you help me to learn more?
(Other definitions for charcoal that I've seen before include "Black carbon produced by burning wood" , "Artist's black material" , "Very dark gray color" , "What gets Barbie going" , "Fuel used for drawing" .)