Time to mature (3)
I believe the answer is:
age
I believe this is a double definition.
'time' is the first definition.
(an age is a period of time)
'mature' is the second definition.
(synonyms)
'to' acts as a link.
(Other definitions for age that I've seen before include "Period piece" , "Maturity" , "Period of time" , "Period of history" , "Long period" .)