Nouveaux-riches are opposing down-ends (8)
I believe the answer is:
upstarts
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for upstarts that I've seen before include "Braggarts" , "Arrogant people just arrived in high positions" , "parvenues" , "People who have risen suddenly to authority, arrogant with it" , "Arrogant types" .)