Annoying person or thing (8)
I believe the answer is:
nuisance
I believe this is a double definition.
'annoying person' is the first definition.
(I've seen this before)
'thing' is the second definition.
(I have seen 'Troublesome thing ' mean 'nuisance' so perhaps 'thing' could also mean 'nuisance')
(Other definitions for nuisance that I've seen before include "One causing annoyance" , "Pest, pain in the neck" , "Tiresome person or event" , "Annoying person/thing" , "'Pest, annoyance (8)'" .)