Choreographer Frederick ____ succeeded Ninette de Valois as director of the Royal Ballet (6)
I believe the answer is:
ashton
(Other definitions for ashton that I've seen before include "- - -under-Lyne" , "Lancashire town - dancer - Rugby coach" , "Sir Frederick -; Eng. ballet dancer, choreographer" , "Sir Frederick -, 20th century choreographer, dancer" , "Sir Frederick -, English choreographer/dancer" .)