Old rulers, never red (5)

I believe the answer is:

tsars

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'old rulers' is the definition.
(as in the tsars of Russia)

I don't understand the remainder of the clue.

(Other definitions for tsars that I've seen before include "Old monarchs" , "Russian emperors" , "Old Russia's rulers" , "Old Russian rulers" .)

I've seen this clue in the Evening Standard.

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