Room under the roof (5)
I believe the answer is:
attic
'room under the 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 "Top storey" , "Athenian Greek" , "Ancient Greek dialect - top room" , "Area at the top of the house" , "Dusty room" .)