Unassuming character sounding buzzer (9)

I believe the answer is:

humblebee

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'buzzer' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

'unassuming character sounding' is the wordplay.
'unassuming' becomes 'humble' (I've seen this in another clue).
'character' becomes 'B'.
'sounding' shows a homophone (sound like).
'b' sounds like 'bee'.
'humble'+'bee'='HUMBLEBEE'

Can you help me to learn more?

I've seen this clue in The Times.

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