Son enjoying a spliff, adding more to burn (7)

I believe the answer is:

stoking

'adding more to burn' is the definition.
(as in stoking a fire)

'son enjoying a spliff' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'enjoying a spliff' becomes 'toking' (toke can mean to smoke cannabis).
's'+'toking'='STOKING'

I've seen this clue in The Guardian.

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