Run in next race (5)
I believe the answer is:
extra
'run' is the definition.
(cricket run)
'in next race' is the wordplay.
'in' indicates the answer is hidden within the clue.
'EXTRA' can be found hidden inside 'next race'.
(Other definitions for extra that I've seen before include "one added to the score" , "more than required" , "outside" , "Wide, no-ball, leg bye, etc" , "Bit-part actor" .)