Keep talking tediously? Exactly (4,2)

I believe the answer is:

bang on

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But I can't explain it at all! Could you help me understand?

(Other definitions for bang on that I've seen before include "Informally and absolutely accurate; it's explosive" , "Keep talking tediously" , "Talk too long (informal) - exactly (informal)" , "Exactly right; talk tediously (about)" , "Informally quite right - sounds noisy" .)

I've seen this clue in The Sun.

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