Mostly elegant character from Greece (3)
I believe the answer is:
chi
'character from greece' is the definition.
(chi is a Greek letter)
'mostly elegant' is the wordplay.
'mostly' means to remove the last letter (most but not all of the word).
'elegant' becomes 'chic' (chic means fashionable or elegant).
'chic' with its last letter taken away is 'CHI'.
(Other definitions for chi that I've seen before include "Greek letter; Chinese life force" , "character from Euripides?" , "Letter written by European" , "Greek X" , "The 22nd letter of Greek alphabet" .)