Initial jump? (5)

I believe the answer is:
start
This clue could be a double definition.
'initial' is the first definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'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 "Move quickly < when surprised" , "Initiate" , "Begin with sudden movement of surprise" , "Jerk" , "Opening - jump" .)
