One's opening jump? (5)
I believe the answer is:
start
This could be a double definition.
'one's opening' is the first definition.
'start' can be an answer for 'opening' (both can mean the beginning). I am unsure of the 'one's' bit.
'jump?' is the second definition.
(as in starting or jumping in fear)
Can you help me to learn more?
(Other definitions for start that I've seen before include "Begin to recoil?" , "Begin; flinch" , "Set in motion" , "lead" , "Commence" .)