Rehearsal for smuggling booze? (3,3)

I believe the answer is:

dry run

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'rehearsal' is the definition.
(synonyms)

I can't explain the remainder of the clue.

(Other definitions for dry run that I've seen before include "Kind of rehearsal like thirsty trot" , "Dummy trial on thirsty trot?" , "A dummy test - sounds thirsty" , "Procedure rehearsal" , "Practice session in preparation for public performance" .)

I've seen this clue in The Guardian.

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