More take part in the next race (5)
I believe the answer is:
extra
'more' is the definition.
(I've seen this in another clue)
'part in the next race' is the wordplay.
'part in' says the answer is hidden in the clue.
'EXTRA' is hidden within 'next race'.
'take' is the link.
(Other definitions for extra that I've seen before include "Supplemental" , "An additional thing" , "Bit part actor" , "like one of the crowd" , "Minor actor in crowd scene" .)