Repetition of extra terminal message (3-3)

I believe the answer is:

bye-bye

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'repetition of extra terminal message' is the definition.
'bye-bye' can be an answer for 'message' (bye-bye is a kind of message). I'm not certain of the 'repetition of extra terminal' bit.

'extra terminal message' is the wordplay.
'extra' becomes 'bye' (cricket term).
'terminal message' becomes 'bye' (bye is a kind of message. I am not sure about the 'terminal' bit.).
'bye'+'bye'='BYE-BYE'

Can you help me to learn more?

(Other definitions for bye-bye that I've seen before include "Childish farewell" , "Informal repetitive farewell" , "Au revoir for juniors?" , "So long" , "See you" .)

I've seen this clue in The Times.

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