Pointer to what the heckler tries to do (6)
I believe the answer is:
needle
'pointer' is the definition.
(as in a needle on a compass)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for needle that I've seen before include "has only one eye" , "Irritate, goad" , "Leaf of a 15 across" , "Unnecessary" , "It's difficult to find one in a haystack" .)