Lady, perhaps, noticed a knight returning to top of castle to overturn dark, flammable substance (10)
I believe the answer is:
aristocrat
'lady perhaps' is the definition.
(lady is a kind of aristocrat)
'noticed a knight returning to top of castle to overturn dark flammable substance' is the wordplay.
I cannot quite see how this works, but
'a' is within the answer.
'to' is found in the answer.
'castle' could be 'r' (abbreviation for rook/castle in chess) and 'r' is located in the answer.
'substance' could be 'sc' (Sc is an example) and 'sc' is present in the leftover letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for aristocrat that I've seen before include "Member of the upper class" , "Patrician" , "Noble" , "What's listed in Debrett" , "Nob" .)