Little quibble (3)
I believe the answer is:
nit
'little quibble' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nit that I've seen before include "Young louse" , "Parasite's egg made of tin" , "Cause of much head-scratching" , "Louse; fool" , "Egg of parasitic insect" .)