Window over a door (7)
I believe the answer is:
transom
'window over a door' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for transom that I've seen before include "something seen in the window" , "Cross-beam" , "bolstering member" , "Horizontal bar across door for matrons" , "Bar above window or door" .)