It's almost noon, soon (6)
I believe the answer is:
nearly
'it's almost' is the definition.
('nearly' can be a synonym of 'almost')
'noon soon' is the wordplay.
'noon' becomes 'n'.
'soon' becomes 'early' (I've seen this before).
'n'+'early'='NEARLY'
(Other definitions for nearly that I've seen before include "Close" , "approximately" , "Almost, well-nigh" , "Give out a bright light" , "Almost, not quite" .)