Nervous about the hazards in steeplechasing? (5)

I believe the answer is:

jumpy

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'nervous' is the definition.
(synonyms)

I don't understand the remainder of the clue.

(Other definitions for jumpy that I've seen before include "Anxious, uneasy" , "Nervous (as beans or fleas?)" , "Jittery" , "On edge" .)

I've seen this clue in the Evening Standard.

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