Foreign currency Spanish gents used (not ores) (3)

I believe the answer is:

sen

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'foreign currency' is the definition.
(I've seen this in another clue)

I don't understand how the rest of the clue works.

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(Other definitions for sen that I've seen before include "Very small change for Japanese" , "three quarters?" , "very little change in the Far East" , "ready for Japan" , "Fraction of yen" .)

I've seen this clue in The Times.

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