Greek character, artist, left a sort of painting (5)
I believe the answer is:
mural
'a sort of painting' is the definition.
'greek character artist left' is the wordplay.
'greek character' becomes 'mu' (letter from the Greek alphabet).
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'left' becomes 'l' (common abbreviation).
'mu'+'ra'+'l'='MURAL'
(Other definitions for mural that I've seen before include "Wall decoration" , "Wall-painting" , "Large wall painting" , "Artwork" , "Drawing on a wall" .)