Window projecting from a sloping roof (6)
I believe the answer is:
dormer
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">window projecting from a sloping roof</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(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" .)