Kind of window (6)
I believe the answer is:
dormer
'kind of window' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for dormer that I've seen before include "Light" , "Window projecting vertically from a sloping roof" , "Upright window built out from a sloping roof" , "Type of window set in sloping roof" , "Window under gable on sloping roof" .)