Many are different when the tail’s docked (6)

I believe the answer is:

divers

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'many' is the definition.
(thesaurus)

I cannot understand how the remainder of the clue works.

(Other definitions for divers that I've seen before include "competitors at the Olympic Games?" , "ducks" , "people taking the plunge" , "people going to bed?" , "Various for underwater workers?" .)

I've seen this clue in the Evening Standard.

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