Badinage about knees-up we hear (8)
I believe the answer is:
repartee
'badinage' is the definition.
(I've seen this before)
'about knees-up we hear' is the wordplay.
I cannot really see how this works, but
'about' could be 're' ('re' means regarding or about) and 're' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for repartee that I've seen before include "Quick witty replies" , "Snappy answer" , "Witty exchange" , "Banter - pear tree (anag)" , "Badinage" .)