A question of property (5)
I believe the answer is:
whose
'a question of property' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'question of property' is the wordplay.
'question' becomes 'who' (who is a question word).
'of property' becomes 'se' (I am not sure about this - if you are sure you should believe this answer much more).
'who'+'se'='WHOSE'
Can you help me to learn more?
(Another definition for whose that I've seen is " Of which person".)