Reverberation upset grand toff (4)

I believe the answer is:

bong

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'reverberation upset grand toff' is the definition.
I can't judge whether this defines the answer.

'upset grand toff' is the wordplay.
'upset' says the letters should be written backwards.
'grand' becomes 'g' (G is short for grand as in a thousand).
'toff' becomes 'nob' (UK slang for a wealthy or upper-class person).
'g'+'nob'='gnob'
'gnob' reversed gives 'BONG'.

Can you help me to learn more?

(Another definition for bong that I've seen is " pipe".)

I've seen this clue in The Times.

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