Additional entrant in the next race (5)
I believe the answer is:
extra
'additional' is the definition.
(extra means additional or surplus)
'in the next race' is the wordplay.
'in' says the answer is hidden in the clue.
'EXTRA' is hidden in the letters of 'next race'.
'entrant' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for extra that I've seen before include "Crowd-scene actor" , "Additional, more than expected" , "eg Wide; additional" , "Bye or wide, for example" , "An additional thing" .)