Not late but nearly lost a point (5)
I believe the answer is:
early
'not late' is the definition.
('early' is the opposite to 'late')
'nearly lost a point' is the wordplay.
'lost' indicates named letters should be taken away.
'a point' becomes 'N' (N is an example).
'nearly' with 'n' taken away is 'EARLY'.
'but' is the link.
(Other definitions for early that I've seen before include "Untimely" , "Premature" , "'The ..... bird catches the worm'" , "at start of day" , "In good time" .)