Nicker, small amount of money (6)

I believe the answer is:

copper

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'money' is the definition.
(I have seen 'Little money' mean 'copper' so perhaps 'money' could also mean 'copper')

I cannot understand how the rest of the clue works.

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(Other definitions for copper that I've seen before include "detector?" , "Element; butterfly" , "Daily Beast proprietor" , "An element; small coin" , "Metallic element for a British policeman" .)

I've seen this clue in The Guardian.

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