Toasted William the Just! (5)

I believe the answer is:

brown

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'just' is the definition.
Both the answer and definition are adjectives. Maybe there's a link between them I don't understand?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for brown that I've seen before include "Colour (of the PM?)" , "Rugby hero" , "Kind of sweetener" , "Four-point ball" , "Colour of earth" .)

I've seen this clue in the Evening Standard.

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