Talk for too long? That's absolutely right! (4,2)
I believe the answer is:
bang on
'absolutely right' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for bang on that I've seen before include "Informally, absolutely correct - may be noisy" , "Absolutely right - sounds noisy" , "with great accuracy" , "Keep talking tediously" , "Talk too long (informal) - exactly (informal)" .)