Greek character contributing to Attic history (3)
I believe the answer is:
chi
'greek character' is the definition.
(letter from the Greek alphabet)
'contributing to attic history' is the wordplay.
'contributing to' says the answer is hidden in the clue.
'CHI' is hidden within 'attic history'.
(Other definitions for chi that I've seen before include "Greek X" , "Letter written by European" , "Twenty-second Greek letter" , "The life force, according to traditional Chinese medicine" , "The 22nd letter of Greek alphabet" .)