Long time back, Everyman's included as potential success (7)
I believe the answer is:
nominee
'potential success' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'long time back everyman's included' is the wordplay.
'long time' becomes 'eon' (eon is a kind of long time).
'back' is a reversal indicator.
'everyman's' becomes 'mine' (where the crossword setter is 'Everyman').
'included' indicates putting letters inside.
'eon' written backwards gives 'noe'.
'noe' enclosing 'mine' is 'NOMINEE'.
'as' acts as a link.
Can you help me to learn more?
(Other definitions for nominee that I've seen before include "One named to act for another" , "someone to act for them" , "he may shield one" , "One named as candidate" , "No real owner" .)