Woman left behind when knight's thrown out of hole in the wall? (5)
I believe the answer is:
widow
'woman left' is the definition.
(woman whose husband has died)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for widow that I've seen before include "One losing husband" , "See 20" , "The Merry --, operetta" , "Woman who has lost her husband" , "Bereaved" .)