Announced calm period in broadcast (10)

I believe the answer is:

proclaimed

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'announced' is the definition.
(I know that announced can be written as proclaimed)

'calm period in broadcast' is the wordplay.
'calm period' can be anagrammed to 'PROCLAIMED'.
Though, I'm not clear how the anagram is indicated.

Can you help me to learn more?

(Another definition for proclaimed that I've seen is " Lauded".)

I've seen this clue in The Guardian.

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