Pernickety person (7)
I believe the answer is:
fusspot
'pernickety person' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for fusspot that I've seen before include "Over-fastidious person" , "Person hard to please" , "Hard-to-please person" , "Nervously agitating type" , "one worrying about trifles" .)