Once more is providing an energy-reducing device (10)

I believe the answer is:

economiser

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'an energy-reducing device' is the definition.
I can't tell whether this defines the answer.

'once more is providing' is the wordplay.
'providing' is an anagram indicator.
'once'+'more'+'is'='oncemoreis'
'oncemoreis' anagrammed gives 'ECONOMISER'.

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I've seen this clue in the Sydney Morning Herald.

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