Chatter of an incidental kind (4)
I believe the answer is:
talk
'chatter' is the definition.
(I know this)
'of an incidental kind' is the wordplay.
'of' indicates a hidden word.
'TALK' is hidden in the letters of 'incidental kind'.
(Other definitions for talk that I've seen before include "Speak frankly (about the Christmas dinner?)" , "Gossip - lecture" , "that's said to be cheap" , "Discussion" , "Discourse" .)