Be old enough to succeed largely as a revolutionary (4,2,3)
I believe the answer is:
come of age
'largely as a revolutionary' is the definition.
I can't judge whether this definition defines the answer.
'be old enough to succeed' is the wordplay.
'be' becomes 'come' (coming is a kind of being).
'old enough' becomes 'of age' (having come of age).
'to succeed' says to put letters next to each other.
'come'+'ofage'='COME OF AGE'
Can you help me to learn more?
(Other definitions for come of age that I've seen before include "Reach adulthood" , "Reach maturity with rights to vote etc" , "Reach adult status, perhaps 21" , "Attain maturity" , "Grow up" .)