Repartee (6)
I believe the answer is:
banter
'repartee' is the definition.
(I know that banter is a type of repartee)
This is the entire clue.
(Other definitions for banter that I've seen before include "Tease in good-humoured way" , "Rail" , "Good-natured teasing" , "Playfully teasing remarks" , "Playful exchanges" .)