Pesters, irritates (6)
I believe the answer is:
annoys
I believe this is a double definition.
'pesters' is the first definition.
(I've seen this before)
'irritates' is the second definition.
(I've seen this in another clue)
(Other definitions for annoys that I've seen before include "Narks" , "Irritates, bothers" , "Nettles" , "'Irritates, irks (6)'" , "Irks, vexes" .)