Motor race among leaders of drivers yesterday (4)
I believe the answer is:
indy
'motor race' is the definition.
(nickname of the Indianapolis 500-Mile Race)
'among leaders of drivers yesterday' is the wordplay.
'among' becomes 'in' (I've seen this in other clues).
'leaders of' indicates taking the first letters.
The initial letters of 'drivers yesterday' is 'dy'.
'in'+'dy'='INDY'
(Other definitions for indy that I've seen before include "- - Car racing (in US)" , "Form of competition between drivers" , "US motor-racing" , "Type of motor racing" , "500-mile US motorcar race" .)