Fuel used for heating a stove (3)
I believe the answer is:
gas
'fuel' is the definition.
(gas is a fuel)
'used for heating a stove' is the wordplay.
'used for' indicates a hidden word.
'GAS' is hidden within 'heating a stove'.
(Other definitions for gas that I've seen before include "Hydrogen possibly" , "Something that is neither solid not liquid" , "Hydrogen or methane, say" , "Eg, hydrogen" , "eg Helium" .)