Neither in backed out for anaesthetic (5)

I believe the answer is:

ether

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'for anaesthetic' is the definition.
(ether is a kind of anaesthetic)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for ether that I've seen before include "Once widely-used anaesthetic" , "Volatile solvent" , "Volatile organic liquid once used as a general anaesthetic" , "Gas - air - space" , "Anaesthetic; clear sky (poetic)" .)

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

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