Split points, being mature (5)
I believe the answer is:
ripen
'mature' is the definition.
(ripening is a kind of maturing)
'split points' is the wordplay.
'split' becomes 'rip' ('rip' can be a synonym of 'split').
'points' becomes 'en' (**).
'rip'+'en'='RIPEN'
'being' acts as a link.
(Other definitions for ripen that I've seen before include "Become ready to harvest" , "Grow older" , "Develop fully" , "Come to maturity like fruit" , "Become ready to pick" .)