Black veil must be worn (4)

I believe the answer is:

evil

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'black' is the definition.
(similar in meaning)

'veil must be worn' is the wordplay.
'veil' anagrams to 'EVIL'.
But, I'm not clear how this is indicated.

Can you help me to learn more?

(Other definitions for evil that I've seen before include "Profoundly wicked" , "Excellent" , "Depravity, wickedness" , "'The ... that men do lives after them' (Shakespeare)" , "Nefarious" .)

I've seen this clue in The Times.

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