Room just under a roof (5)
I believe the answer is:
attic
'room just under a roof' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for attic that I've seen before include "Athenian - garret" , "The highest room" , "cockloft" , "Room inside a building's roof space" , "Athenian Greek" .)