What can attract good fortune? (9,6)

I believe the answer is:

horseshoe magnet

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'fortune?' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see an association between them that I don't see?

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

Can you help me to learn more?

(Another definition for horseshoe magnet that I've seen is " what's attractive".)

I've seen this clue in The Times.

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