More in next race (5)
I believe the answer is:
extra
'more' is the definition.
(thesaurus)
'in next race' is the wordplay.
'in' indicates a hidden word.
'EXTRA' is hidden in the letters of 'next race'.
(Other definitions for extra that I've seen before include "leg bye perhaps" , "more than is necessary" , "late edition" , "Cricket run; unusually" , "23 player?" .)