It can come from coal or smouldering ashes (3)
I believe the answer is:
gas
'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" .)