Jumper that says "Track official" (7)
I believe the answer is:
starter
'official' is the definition.
(starter is a kind of official)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for starter that I've seen before include "Race gun firer" , "cooking served first?" , "Appetiser" , "Type of home" , "Beginner, or opening course of meal" .)