Jump start (6)

I believe the answer is:

spring

This clue is a double definition.

'jump' is the first definition.
(spring is a kind of jump)

'start' is the second definition.
(both can mean to jump or be startled)

(Other definitions for spring that I've seen before include "Season of growth" , "Pounce -- pogo stick part" , "Bound; source" , "past February is it?" , "Water gushing" .)

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

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