Gas company in charge of heat (7)
I believe the answer is:
caloric
'of heat' is the definition.
(I've seen this in another clue)
'gas company in charge' is the wordplay.
I cannot really understand how this works, but
'gas' could be 'calor' (I have seen 'liquid gas' mean 'calor' so perhaps 'gas' could also mean 'calor') and 'calor' is found within the answer.
'in charge' could be 'ic' (abbreviation for 'in charge') and 'ic' is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for caloric that I've seen is " Thermal".)