Greek character has a large medicine bottle (5)
I believe the answer is:
phial
'medicine bottle' is the definition.
(I've seen this before)
'greek character has a large' is the wordplay.
'greek character' becomes 'phi' (letter from the Greek alphabet).
'has' means one lot of letters go next to another.
'large' becomes 'l'.
'phi'+'a'+'l'='PHIAL'
(Other definitions for phial that I've seen before include "Ampoule" , "Small bottle (containing a drug)" , "Small bottle for potions etc" , "Small bottle for liquids" , "Source of medicine" .)