One of the angry-looking people on the left? (3)

I believe the answer is:

red

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'on the left?' is the definition.
(red can mean leftwing)

I cannot understand how the remainder of the clue works.

(Other definitions for red that I've seen before include "Blushing" , "Warning light colour" , "Florid" , "Inflamed" , "Carmine" .)

I've seen this clue in the Evening Standard.

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