Rages if source of heat is changed (3,4)
I believe the answer is:
gas fire
'heat is changed' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'rages if source of' is the wordplay.
'source of' indicates anagramming the letters.
'rages'+'if'='ragesif'
'ragesif' anagrammed gives 'GAS FIRE'.
Can you help me to learn more?
(Other definitions for gas fire that I've seen before include "source of heat" , "Domestic form of heater" , "Glower" .)