Pain in the neck (5)
(Other definitions for nuisance that I've seen before include "See 16" , "Annoying thing/person" , "Tiresome person or event" , "Source of irritation, person or thing" , "Bothersome pest" .)
'pain in the neck' is the definition.
(irritant is a kind of pain in the neck)
This is the entire clue.
(Other definitions for irritant that I've seen before include "Cause of itch" , "Source of continual annoyance" , "Annoying thing" , "Something that chafes or annoys" , "distraction" .)
'pain in the neck' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for crick that I've seen before include "Wrench (neck or back)" , "Muscle spasm in the neck" , "Pain in the neck" , "Neck injury" , "Sort of cramp" .)
'pain in the neck' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for annoyance that I've seen before include "Irritation, vexation" , "Feeling of slight anger" , "(Anger at) harassment" , "trouble" , "Source of anger" .)