Belief in credit notes (5)
I believe the answer is:
creed
'belief' is the definition.
(creed is a kind of belief)
'credit notes' is the wordplay.
'credit' becomes 'cre' (I can't justify this - if you can you should believe this answer much more).
'notes' becomes 'ed'.
'cre'+'ed'='CREED'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for creed that I've seen before include "Statement of belief" , "System of religious principles" , "restricted set of principles" , "teleprinter" , "Church doctrine" .)