Casual conversation (4)
'casual conversation' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for chat that I've seen before include "tittle-tattle" , "waffle?" , "Have friendly informal conversation" , "Casual conversation" , "Small songbird of the thrush family" .)
(Other definitions for chinwag that I've seen before include "Chat (slang)" , "Conversation (slang)" , "Can Whig have an informal chat?" , "Talk (colloq.)" , "Appoint" .)