Time to get ahead with new heart (3)
I believe the answer is:
eon
'time' is the definition.
(I know that eon is a type of geologic time)
'ahead with new heart' is the wordplay.
'ahead' becomes 'on' (synonyms).
'with' is a charade indicator (letters next to each other).
'heart' indicates the central letters.
The central letter of 'new' is 'e'.
'on' put after 'e' is 'EON'.
'to get' is the link.
(Other definitions for eon that I've seen before include "Vast age; eternity" , "Era" , "Age, epoch" , "Huge time period" , "Prolonged period" .)