Belief in buying power (6)
I believe the answer is:
credit
This clue might be a double definition.
'belief' is the first definition.
(thesaurus)
'buying power' is the second definition.
'credit' can be an answer for 'power' (thesaurus). I am unsure of the 'buying' bit.
'in' is the link.
Can you help me to learn more?
(Other definitions for credit that I've seen before include "Source of pride; account entry" , "Belief - trust - favourable acknowledgment" , "this is a decent exam grade" , "Believe the time to pay?" , "Acknowledgment, recognition or praise" .)