Red number (8)

I believe the answer is:

cardinal

This clue is a double definition.

'red' is the first definition.
(I know that cardinal is a type of red)

'number' is the second definition.
(I know that cardinal is a type of number)

(Other definitions for cardinal that I've seen before include "of the highest importance" , "Main - church dignitary" , "Key" , "of prime importance" , "Vivid red of a senior bishop?" .)

I've seen this clue in The Telegraph, The Washington Post and the L.A. Times Daily.

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