Greek king doomed to forever roll a boulder uphill (8)
I believe the answer is:
sisyphus
(Other definitions for sisyphus that I've seen before include "Mythological Greek king doomed to forever roll a boulder uphill" , "He had an endless job" , "Legendary Greek king doomed to forever roll a boulder uphill" , "Greek king fated ever to roll a stone uphill in Hades" , "Plead case" .)