English auntie dismisses conservative retreat (3)

I believe the answer is:

ebb

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'retreat' is the definition.
(ebb can mean to fall back or retreat)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for ebb that I've seen before include "Fall back" , "(Of tidewater) recede" , "Outward flow of the tide" , "(Sea) recede" , "Tidal retreat" .)

I've seen this clue in The Guardian.

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