Does he make the competitors jump to his orders? (7)
I believe the answer is:
'does he make the competitors' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'jump to his orders?' is the wordplay.
'jump' becomes 'start' (as in starting or jumping in fear).
'to his orders?' becomes 'er' (I am not sure about this - if you are sure you should believe this answer much more).
Can you help me to learn more?
(Other definitions for starter that I've seen before include "Type of home" , "Appetiser" , "Beginner, or opening course of meal" , "Hors d'oeuvre" , "One giving signal to begin race" .)