Yet this horse keeps going (6)
I believe the answer is:
stayer
'yet this horse keeps going' is the definition.
The answer and definition can be both animals as well as being singular nouns.
Maybe there's a link between them I don't understand?
This is the entire clue.
Can you help me to learn more?
(Other definitions for stayer that I've seen before include "being in for the long run" , "One likely to carry on" , "marathon man" , "Long-distance runner, rather than sprinter" , "Persistent person" .)