Caught in the end, marathon unfinished -- athletic event (9)
I believe the answer is:
decathlon
'athletic event' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for decathlon that I've seen before include "sporting contest" , "Athletic event" , "Competition comprising ten events" , "Latched on to athletic competition of 10 events" , "Versatile Olympic event" .)