Be a Nosy Parker (4,2)
I believe the answer is:
butt in
'be a nosy parker' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for butt in that I've seen before include "Thrust oneself into a conversation" , "Interrupt a conversation" , "Interrupt or meddle - like goat?" , "Break into a conversation" , "Interrupt, intrude" .)