Harass a speaker (6)
I believe the answer is:
heckle
'harass a speaker' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for heckle that I've seen before include "Barrack speaker" , "Verbally interrupt performer" , "Loudly interrupt a public meeting" , "disrupt meeting" , "Harass a speaker" .)