Window projecting from a sloping roof (6)
I believe the answer is:
dormer
'window projecting from a sloping roof' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for dormer that I've seen before include "Bungalow with a vertical window in a sloping roof" , "Window fitted vertically onto a sloping roof." , "Type of window set in sloping roof" , "Light" , "Window under gable on sloping roof" .)