They impressed old sailors (5,5)

I believe the answer is:

press gangs

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This could be a double definition.

'they' is the first definition.
Both the answer and definition are plural nouns.
Perhaps you can see a link between them that I can't see?

'impressed old sailors' is the second definition.
Although both the answer and definition are plural nouns, I can't see how they can define each other.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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