In the descent, he’s ahead of you (8)
I believe the answer is:
ancestor
'in the descent he's ahead of you' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
This is all the clue.
Can you help me to learn more?
(Other definitions for ancestor that I've seen before include "Person from whom one is descended" , "Antecedent, forebear" , "not being of the modern generation" , "Enactors (anag)" , "descent comes from one" .)