One hears a rumpus is vexatious (6)

I believe the answer is:

annoys

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'a rumpus is vexatious' is the definition.
I can't tell whether this definition defines the answer.

'one hears' is the wordplay.
'one' becomes 'an' (an apple is one apple).
'hears' becomes 'noys' (I can't justify this - if you can you should give a lot more credence to this answer).
'an'+'noys'='ANNOYS'

Can you help me to learn more?

(Other definitions for annoys that I've seen before include "Narks" , "Hacks off" , "Nettles" , "is vexing" , "Irritates, vexes" .)

I've seen this clue in The Globe and Mail.

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