One powerful goal, with rich result (8)
I believe the answer is:
oligarch
'one powerful' is the definition.
(I know this)
'goal with rich result' is the wordplay.
'with' is a charade indicator (letters next to each other).
'result' indicates an anagram (I've seen 'result of' mean this).
'goal' put after 'rich' is 'richgoal'.
'richgoal' with letters rearranged gives 'OLIGARCH'.
(Other definitions for oligarch that I've seen before include "member of small ruling class" , "Member of a small governing group" , "member of ruling minority" , "Mega-rich Russian with political influence" , "Rich Russian with political influence" .)