To prevent overheating use this - not coal anyway (7)
I believe the answer is:
coolant
'to prevent overheating use this' is the definition.
The definition suggests a singular noun which matches the answer.
'not coal anyway' is the wordplay.
'anyway' indicates anagramming the letters.
'not'+'coal'='notcoal'
'notcoal' with letters rearranged gives 'COOLANT'.
Can you help me to learn more?
(Other definitions for coolant that I've seen before include "part of heat exchanger" , "Additive in radiator that stops engine overheating" , "One should stop overheating" , "This takes heat out of situation" , "used to prevent overheating" .)