A fen, mist having moved, clear (8)

I believe the answer is:

manifest

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'clear' is the definition.
(synonyms)

'a fen mist having moved' is the wordplay.
'a fen mist' can be anagrammed to 'MANIFEST'.
However, I am not sure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for manifest that I've seen before include "Ship's document; plain" , "show" , "Express" , "Become apparent" , "Cargo list - it's quite clear" .)

I've seen this clue in The Times.

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