Window when framed by putty? (8)
I believe the answer is:
casement
'window' is the definition.
(casement is a kind of window)
'when framed by putty?' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'framed by' is an insertion indicator.
'putty?' becomes 'cement' (putty is a kind of cement).
'as' inserted inside 'cement' is 'CASEMENT'.
(Other definitions for casement that I've seen before include "Poetic word for window" , "Window that opens with hinges on side, like a door" , "Vertically-hinged window" , "Window opening on a vertical hinge" , "Hinged window-frame" .)