By getting ahead, he became president (5)
I believe the answer is:
peron
'president' is the definition.
(I have seen 'Argentinian president ' mean 'peron' so perhaps 'president' could also mean 'peron')
'by getting ahead' is the wordplay.
'by' becomes 'per' (I've seen this in another clue).
'getting' says to put letters next to each other.
'ahead' becomes 'on' (synonyms).
'per'+'on'='PERON'
'he became' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for peron that I've seen before include "Prone to being an Argentine president" , "Surname of Evita of the musical" , "Juan, maybe" , "Argentinian dictator, 1946-55" , "Former Argentinian leader" .)