Pin bulk of credit crunches on former financial guide (5,5)

I believe the answer is:

price index

I'm a little stuck... Click here to teach me more about this clue!

'pin bulk of credit crunches on former' is the definition.
I can't tell whether this defines the answer.

'financial guide' is the wordplay.
'financial' becomes 'price' (I am not sure about this - if you are sure you should believe this answer much more).
'guide' becomes 'index' (I have seen 'Alphabetical guide ' mean 'index' so perhaps 'guide' could also mean 'index').
'price'+'index'='PRICE INDEX'

Can you help me to learn more?

I've seen this clue in The Independent.

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