He's one who's come to the fore (4)
I believe the answer is:
ivan
'he's' is the definition.
'one who's come to the fore' is the wordplay.
'one' becomes 'an' (an apple is one apple).
'who's come' becomes 'iv' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to the fore' is a charade indicator (letters next to each other).
'an' after 'iv' is 'IVAN'.
Can you help me to learn more?
(Other definitions for ivan that I've seen before include "Russian boy's name" , "terrible tyrant" , "man who had a terrible reputation" , "One Day in the Life of - Denisovich (Solzhenitsyn)" , "'Terrible' emperor of Russia" .)