Badger, deer, tailless horse (6)

I believe the answer is:

harass

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'badger' is the definition.
(synonyms)

I don't understand the rest of the clue.

(Other definitions for harass that I've seen before include "Pester, badge" , "Bother and annoy continuously" , "Make repeated attacks on" , "Badger, antagonise" , "Trouble and annoy continually" .)

I've seen this clue in The Times and The Sunday Times.

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