Nearly, not quite (6)
I believe the answer is:
almost
This clue is a double definition.
'nearly' is the first definition.
(synonyms)
'not quite' is the second definition.
(I've seen this before)
(Other definitions for almost that I've seen before include "Slightly short of" , "Well-nigh" , "As good as" , "Virtually" , "Nearly, not quite" .)