It's good as a source of heat (3)

I believe the answer is:

gas

I'm a little stuck... Click here to teach me more about this clue!

'a source of heat' is the definition.
I can't judge whether this defines the answer.

'it's good as' is the wordplay.
'it's good' becomes 'g' (abbreviation).
'g'+'as'='GAS'

Can you help me to learn more?

(Other definitions for gas that I've seen before include "Petrol (US)" , "Possibly noble" , "It may be natural" , "State of matter not solid or liquid" , "Something that is neither solid not liquid" .)

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.