Irritation, pest (8)
I believe the answer is:
nuisance
I believe this clue is a double definition.
'irritation' is the first definition.
(thesaurus)
'pest' is the second definition.
(both can mean an annoying person)
(Other definitions for nuisance that I've seen before include "Trouble" , "Source of irritation, person or thing" , "Tiresome person or event" , "Bothersome annoying person" , "One causing annoyance" .)