Although he keeps going, he remains where he is (6)
I believe the answer is:
stayer
'although he keeps going he remains where he is' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
This is the entire clue.
Can you help me to learn more?
(Other definitions for stayer that I've seen before include "One with stamina" , "Long-distance runner, rather than sprinter" , "Horse with stamina" , "marathon man" , "Person with perseverance" .)