Ambitious partisan on the move (8)
I believe the answer is:
aspirant
'ambitious' is the definition.
('aspirant' can be similar in meaning to 'ambitious')
'partisan on the move' is the wordplay.
'on the move' is an anagram indicator.
'partisan' anagrammed gives 'ASPIRANT'.
(Other definitions for aspirant that I've seen before include "One hoping for success" , "His desire could make him" , "Partisan may be person with high ambition" , "Ambitious" , "Seeker after success" .)