Contestant who simply can't go another round (8)
I believe the answer is:
finalist
'contestant' is the definition.
(I know that finalist is a type of contestant)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for finalist that I've seen before include "Competitor who reaches the last stage" , "Participant in the last round of a competition" , "One at decisive stage" , "He qualified" , "possible winner" .)