Winner -- a Greek character, always (8)
I believe the answer is:
achiever
'winner' is the definition.
(I know that winner can be written as achiever)
'a greek character always' is the wordplay.
'greek character' becomes 'chi' (letter from the Greek alphabet).
'always' becomes 'ever' (synonyms).
'a'+'chi'+'ever'='ACHIEVER'
(Other definitions for achiever that I've seen before include "One who accomplishes or reaches goal" , "one doing well" , "Person who gets things done" , "Go-getter" , "One who gets things done" .)