Dogmatic, a director in cast (11)
I believe the answer is:
doctrinaire
'dogmatic' is the definition.
(I've seen this before)
'a director in cast' is the wordplay.
'cast' indicates an anagram (letters are dispersed or cast around).
'a'+'director'+'in'='adirectorin'
'adirectorin' with letters rearranged gives 'DOCTRINAIRE'.
(Other definitions for doctrinaire that I've seen before include "Trying to impose beliefs" , "Opinionated" , "Dogmatic" , "not practical" , "Inflexible in applying theory" .)