Opposite talk (8)
I believe the answer is:
converse
This clue is a double definition.
'opposite' is the first definition.
(I've seen this before)
'talk' is the second definition.
(conversing is a kind of talking)
(Other definitions for converse that I've seen before include "Talk together" , "express thoughts and ideas?" , "Opposing" , "Communicate with" , "Discourse" .)