Annoy, vex (8)
I believe the answer is:
irritate
This clue is a double definition.
'annoy' is the first definition.
(I know that annoy can be written as irritate)
'vex' is the second definition.
(I know that vex can be written as irritate)
(Other definitions for irritate that I've seen before include "Make angry or fretful" , "Chafe, annoy" , "Nark" , "Needle" , "Nettle and annoy" .)