Talk about deerstalker perhaps (4)
I believe the answer is:
chat
'talk' is the definition.
(thesaurus)
'about deerstalker perhaps' is the wordplay.
'about' becomes 'c' (abbreviation for 'circa').
'deerstalker perhaps' becomes 'hat' (deerstalker is a kind of hat).
'c'+'hat'='CHAT'
(Other definitions for chat that I've seen before include "Friendly talk" , "A bird; converse" , "Talk amiably - bird" , "Talk casually" , "Bird - talk easily" .)