Mature or just mature over one point (5)
I believe the answer is:
ripen
'mature' is the definition.
(to ripen is to mature)
'mature over one point' is the wordplay.
'mature' becomes 'ripe' (similar in meaning).
'over' means one lot of letters go next to another (in a down clue, some letters go over others).
'one point' becomes 'N' (North).
'ripe'+'n'='RIPEN'
'or just' acts as a link.
(Other definitions for ripen that I've seen before include "Grow older" , "come near to falling" , "Become ready for picking" , "Become ready to eat" , "Become ready to pick" .)