Ripen in time (3)
I believe the answer is:
age
This clue is a double definition.
'ripen' is the first definition.
(I've seen this in another clue)
'time' is the second definition.
(an age is a period of time)
'in' acts as a link.
(Other definitions for age that I've seen before include "Epoch" , "it improves wine" , "Years lived so far" , "Mature, grow in years" , "Long period" .)