Ancient Greek's room (5)
I believe the answer is:
attic
I believe this clue is a double definition.
'ancient greek's' is the first definition.
(Attic is an example)
'room' is the second definition.
(type of room)
(Other definitions for attic that I've seen before include "Athenian - garret" , "Classical" , "Area at the top of the house" , "Classically elegant" , "Small room at the top" .)