Spanish ruler’s cut old bread in Geneva (5)

I believe the answer is:

franc

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'old bread in geneva' is the definition.
I can't tell whether this definition defines the answer.

'spanish ruler's cut' is the wordplay.
'spanish' becomes 'fran' (I can't justify this - if you can you should give a lot more credence to this answer).
'ruler' becomes 'CR' (short for Carolus Rex, King Charles in Latin).
'cut' means to remove the last letter.
'cr' with its final letter removed is 'c'.
'fran'+'c'='FRANC'

Can you help me to learn more?

(Other definitions for franc that I've seen before include "Nonsense (colloq.)" , "Former European currency" , "It's ready" , "Swiss capital" , "Swiss loot" .)

I've seen this clue in The Times.

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