Window when framed by putty, perhaps (8)
I believe the answer is:
casement
'window' is the definition.
(thesaurus)
'when framed by putty perhaps' is the wordplay.
'when' becomes 'as'.
'framed by' means one lot of letters goes inside another.
'putty perhaps' becomes 'cement' (putty is a kind of cement).
'as' inserted within 'cement' is 'CASEMENT'.
(Other definitions for casement that I've seen before include "Poetic word for window" , "Window for the patriot?" , "Window opening on a vertical hinge" , "Sir Roger" , "Roger's window?" .)