In steadfast manner, underlying reforms (10)

I believe the answer is:

enduringly

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'in steadfast manner underlying reforms' is the definition.
I can't tell whether this definition defines the answer.

'underlying reforms' is the wordplay.
'reforms' indicates an anagram.
'underlying' anagrammed gives 'ENDURINGLY'.

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I've seen this clue in The Everyman puzzle in The Observer.

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