Casual talk (4)
'casual talk' 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 "Communication" , "flier" , "Talk casually" , "gas" , "Talk informally; bird" .)
(Other definitions for gossip that I've seen before include "Idle talk and rumour" , "Tittle-tattle" , "Scandalous rumour" , "gas" , "Casual talk about other people" .)