Windsor __ (6)
I believe the answer is:
castle
'windsor' is the definition.
(Windsor Castle is an example)
This is all the clue.
(Other definitions for castle that I've seen before include "Citadel" , "Large fortified building" , "E.g. Harlech, Beaumaris, Windsor" , "''An Englishman's home is his . . .''" , "Stronghold - chessman" .)