Right. A ‘Good-bye abstainer!’ at a knocking sound (3-1-3-3)

I believe the answer is:

rat-a-tat-tat

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'a knocking sound' is the definition.
'rat-a-tat-tat' can be an answer for 'sound' (rat-a-tat-tat is a kind of sound). I'm not sure about the 'a knocking' bit.

'right a good-bye abstainer at' is the wordplay.
'right' becomes 'r' (common abbreviation).
'good-bye' becomes 'ta-ta' (I've seen this in another clue).
'abstainer' becomes 'tt' (I've seen this in other clues).
'r'+'a'+'tata'+'tt'+'at'='RAT-A-TAT-TAT'

Can you help me to learn more?

(Another definition for rat-a-tat-tat that I've seen is " Knocking".)

I've seen this clue in the Sydney Morning Herald.

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