Crossword Genius

Control animal that's kicking its hindquarters (4)

Ross

I believe the answer is:

rein

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'control' is the definition.
(synonyms)

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(Other definitions for rein that I've seen before include "Animal controller" , "Free ... is carte blanche" , "Restriction" , "A means of control" , "Hold back" .)

I've seen this clue in The Independent.
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