Rue tedium, developing a form of hydrogen (9)

I believe the answer is:

deuterium

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'a form of hydrogen' is the definition.
I can't judge whether this defines the answer.

'rue tedium developing' is the wordplay.
'developing' indicates anagramming the letters (letters developed into a new form).
'rue'+'tedium'='ruetedium'
'ruetedium' with letters rearranged gives 'DEUTERIUM'.

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I've seen this clue in The Daily Express.

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