Dear addressees? (4)

I believe the answer is:

sirs

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'dear addressees?' is the definition.
The definition and answer can be both people as well as being plural nouns.
Perhaps there's an association between them I don't understand?

This is all the clue.

Can you help me to learn more?

(Other definitions for sirs that I've seen before include "Knights" , "men" , "Gentlemen" .)

I've seen this clue in the Evening Standard.

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