Nit-picking journo in grocery store? (8)
I believe the answer is:
pedantry
'nit-picking' is the definition.
(I've seen this before)
'journo in grocery store?' is the wordplay.
'journo' becomes 'ed' (I've seen this in other clues).
'in' is an insertion indicator.
'grocery store?' becomes 'pantry' (I've seen this in another clue).
'ed' put into 'pantry' is 'PEDANTRY'.
(Other definitions for pedantry that I've seen before include "Unnecessary formality" , "too much attention to detail" , "Excessive concern with minor rules" , "excessive formality" , "Over-attention to detail" .)