Butterflies fluttering in chalet (6)

I believe the answer is:

thecla

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'butterflies fluttering' is the definition.
The definition suggests a singular noun which matches the answer.

'chalet' is the wordplay.
'chalet' can be anagrammed to 'THECLA'.
Though, I'm not sure how the anagram is indicated.

'in' is the link.

Can you help me to learn more?

I've seen this clue in The Independent.

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