Notes in old currency collected by Paul and mum (9)
I believe the answer is:
memoranda
'notes' is the definition.
(more than one memorandum)
'old currency collected by paul and mum' is the wordplay.
'old currency' becomes 'orand' (I can't explain this - if you can you should believe this answer much more).
'collected by' indicates putting letters inside.
'paul' becomes 'me' (where the crossword setter is 'Paul').
'and' says to put letters next to each other.
'mum' becomes 'ma' (both can mean mother).
'me'+'ma'='mema'
'orand' inserted into 'mema' is 'MEMORANDA'.
'in' is the link.
Can you help me to learn more?
(Other definitions for memoranda that I've seen before include "official minutes" , "Written messages or notes" , "Notes recorded for future use" , "Communications" , "Records" .)