They won't go off with US men that lack energy (4)

I believe the answer is:

duds

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'they' is the definition.
Both the answer and definition are plural nouns.
Maybe they are linked in a way I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for duds that I've seen before include "Failures; clothes" , "Bombs that fail to explode" , "One assumes them" .)

I've seen this clue in The Guardian.

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