Quibbler (6)
I believe the answer is:
pedant
'quibbler' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for pedant that I've seen before include "Know-all who insists on strict observance of rules" , "Nitpicker" , "Particular type" , "Panted over unimaginative scholar." , "Stickler for the rules" .)