Having power and influence over others (8)
I believe the answer is:
dominant
'having power and influence over others' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for dominant that I've seen before include "Having power and influence over others" , "Prevailing or in a commanding position" , "Exercising influence or control" , "Most important or powerful" , "Most influential; fifth of scale" .)