Hot emission in her MOT failing (8)

I believe the answer is:

thermion

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'hot emission' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.

'in her mot failing' is the wordplay.
'failing' indicates anagramming the letters (a failed spelling of the word).
'in'+'her'+'mot'='inhermot'
'inhermot' anagrammed gives 'THERMION'.

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I've seen this clue in The Independent.

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