Banter about BR? (8)

I believe the answer is:

raillery

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This clue could be a double definition.

'banter' is the first definition.
('raillery' can be a synonym of 'banter')

'br?' is the second definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'about' acts as a link.

Can you help me to learn more?

(Other definitions for raillery that I've seen before include "Badinage" , "Light teasing repartee" , "Good-humoured teasing" , "(Example of) banter" , "Playful satire" .)

I've seen this clue in the Evening Standard.

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