Begin to jump (5)
I believe the answer is:
start
I believe this is a double definition.
'begin' is the first definition.
(synonyms)
'jump' is the second definition.
(synonyms)
'to' is the link.
(Other definitions for start that I've seen before include "Onset" , "Initiate" , "Move quickly < when surprised" , "Opening - jump" , "get under way" .)