Split hairs (7)
'split hairs' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for quibble that I've seen before include "Trivial objection" , "Niggle" , "Nit-pick" , "Make trivial objections" , "Petty complaint" .)
(Other definitions for nitpick that I've seen before include "Criticise pettily" , "Make petty criticisms" , "Be fussily pedantic" , "Carp" , "Pedantically find fault" .)