Cake: endless sweetener on the side (7,3)

I believe the answer is:

chelsea bun

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'cake' is the definition.
Both the answer and definition are singular nouns.
Maybe they are linked in a way I don't understand?

'endless sweetener on the side' is the wordplay.
'endless' means to remove the last letter.
'sweetener' becomes 'bung' (both can mean a bribe).
'on' is a charade indicator (letters next to each other).
'the side' becomes 'chelsea' (I've seen this before).
'bung' with its final letter taken off is 'bun'.
'bun' after 'chelsea' is 'CHELSEA BUN'.

Can you help me to learn more?

(Other definitions for chelsea bun that I've seen before include "fruity roll" , "Something sweet" .)

I've seen this clue in The Guardian.

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