Jockey's amendment (5)

I believe the answer is:

rider

I believe this is a double definition.

'jockey's' is the first definition.
(horse rider)

'amendment' is the second definition.
(amendment to a contract)

(Other definitions for rider that I've seen before include "Revere, for example" , "recommendation for mercy?" , "extra weight needed for balance?" , "One may be saddled" , "Clause added to a legal document" .)

I've seen this clue in The Times.

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