Luxuries did hop unpleasantly in gas from fossil fuels (7,7)

I believe the answer is:

sulphur dioxide

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'unpleasantly in gas from fossil fuels' is the definition.
I can't judge whether this defines the answer.

'luxuries did hop' is the wordplay.
'luxuries did hop' anagrams to 'SULPHUR DIOXIDE'.
However, I am unsure how the anagram is indicated.

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

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