We short-circuited race? (4)
I believe the answer is:
indy
'race?' is the definition.
(the Indy 500 or Indianapolis 500 is a motor race)
I cannot understand how the rest of the clue works.
(Other definitions for indy that I've seen before include "US form of motor racing" , "Form of competition between drivers" , "Racing in fast cars" , "A US motor sport" , "US motor-racing" .)