Projecting bay window (5)
I believe the answer is:
oriel
'projecting bay window' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for oriel that I've seen before include "Projecting bay window -- Oxford college" , "Upper room window" , "Projecting window in upper storey" , "polygonal recess" , "One could look through this" .)