Crossword Genius

It can come from coal or smouldering ashes (3)

Ross

I believe the answer is:

gas

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

'it can come from coal' is the definition.
The definition suggests a singular noun but the answer is a plural noun.

'smouldering ashes' is the wordplay.
'GAS' is hidden within the letters.
However, I am uncertain how this is indicated.

'or' acts as a link.

Can you help me to learn more?

(Other definitions for gas that I've seen before include "Chatter (colloq.)" , "idle chit-chat" , "American fuel" , "Something that is neither solid not liquid" , "Oxygen maybe" .)

I've seen this clue in the Evening Standard.
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