The frame of a window (8)
I believe the answer is:
casement
'the frame of a window' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for casement that I've seen before include "Irish nationalist" , "Window for the patriot?" , "Side-opening window" , "Irish Roger" , "Window that opens with hinges on side, like a door" .)