Exhausted, soaked — do's off (4)

I believe the answer is:

used

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'exhausted' is the definition.
(exhaust can mean to use up)

I don't understand the remainder of the clue.

(Other definitions for used that I've seen before include "Subject to exploitation" , "not got directly" , "Manipulated American editor" , "That's not new" , "like majority of cars?" .)

I've seen this clue in The Guardian.

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