"Room at the Top" in Greek (5)
I believe the answer is:
attic
This clue is a double definition.
'room at the top' is the first definition.
(room at the top of a house)
'greek' is the second definition.
(from ancient Athens or Attica)
'in' is the link.
(Other definitions for attic that I've seen before include "High level of" , "Of Athens" , "Upper chamber" , "Lofty room" , "Classically elegant" .)