Galls (4)
I believe the answer is:
irks
'galls' is the definition.
('irk' can be a synonym of 'gall')
This is all the clue.
(Other definitions for irks that I've seen before include "Galls" , "'Irritate, annoy (4)'" , "Annoys, vexes" , "Annoys, irritates" .)