Notes kept in a pocket book perhaps (5,5)
I believe the answer is:
paper money
'book perhaps' is the definition.
The definition and answer can be both related to property as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'notes kept in a pocket' is the wordplay.
I cannot really understand how this works, but
'a' could be 'per' (eg 'one a day' means 'one per day') and 'per' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for paper money that I've seen before include "Banknotes" , "Used as legal tender in place of gold and silver" .)