Annoying thing (4)
I believe the answer is:
pest
'annoying thing' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pest that I've seen before include "Troublesome man or animal" , "Destructive creature" , "Disease with a high death rate" , "Destructive insect or other animal" , "A nuisance - step on it" .)