Sweet tone? (4,4)

I believe the answer is:

eton mess

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

This clue could be a double definition.

'sweet' is the first definition.
(I know that Eton mess is a type of sweet)

'tone?' is the second definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?

Can you help me to learn more?

(Another definition for eton mess that I've seen is " Sweet".)

I've seen this clue in The Guardian.

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