A fiery stimulant left a long time without stress? (10)

I believe the answer is:

accelerant

I'm a little stuck... Click here to teach me more about this clue!

'a fiery stimulant left' is the definition.
The definition suggests a singular noun which matches the answer.

'a long time without stress?' is the wordplay.
'a long' becomes 'l'.
'time' becomes 'era' (an era is a period of time).
'without' is an insertion indicator (some letters go outside or 'without' others).
'stress?' becomes 'accent' (accent can mean to emphasise or stress).
'l'+'era'='lera'
'lera' going within 'accent' is 'ACCELERANT'.

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

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