Former president, Republican, stood for election, originally typecast as deviant (8)
I believe the answer is:
aberrant
'deviant' is the definition.
(synonyms)
'former president republican stood for election originally typecast' is the wordplay.
'former president' becomes 'Abe' (Abraham (Abe) Lincoln).
'republican' becomes 'r' (abbreviation).
'stood for election' becomes 'ran' (as in running for election).
'originally' indicates taking the first letters.
The initial letter of 'typecast' is 't'.
'abe'+'r'+'ran'+'t'='ABERRANT'
'as' acts as a link.
(Other definitions for aberrant that I've seen before include "Departing from type" , "Anomalous" , "Unusual" , "'Deviant, behaviour say (8)'" , "Deviating from the norm, at barren state" .)