Horseless champion succeeded in love (4)
I believe the answer is:
eros
'in love' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for eros that I've seen before include "Arrow shooter" , "asteroid four hundred and thirty three" , "Arrow-shooting god" , "One worshipped" , "Pagan god" .)