Talk constantly heard among talking heads (4)
I believe the answer is:
chat
'talk' is the definition.
(chat can mean to talk)
'constantly heard among talking heads' is the wordplay.
'heads' says to take the initial letters.
The first letters of 'constantly heard among talking' is 'CHAT'.
(Other definitions for chat that I've seen before include "An inconsequential and informal talk" , "Communication" , "Tom in 22 [ALSACE]" , "Talk easily; songbird" , "Casual conversation" .)