Such banter is not good when old (8)

I believe the answer is:

badinage

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'such banter' is the definition.
'badinage' can be an answer for 'banter' (I've seen this before). I'm not certain of the 'such' bit.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for badinage that I've seen before include "Frivolous backchat" , "Frivolous repartee" , "A big Dane given to banter" , "Frivolous talk" , "Backchat, banter" .)

I've seen this clue in The Irish Times.

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