To sleep less backfires, operatically (6)

I believe the answer is:

repose

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'to sleep' is the definition.
(thesaurus)

'less backfires operatically' is the wordplay.
'REPOSE' is hidden back-to-front in amongst the letters.
However, I am unsure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for repose that I've seen before include "calm" , "Relaxation" , "take it easy" , "Lie at rest" , "State of tranquillity" .)

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

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