Commanding, authoritative (11)
I believe the answer is:
magisterial
This clue is a double definition.
'commanding' is the first definition.
(I've seen this before)
'authoritative' is the second definition.
(I've seen this in another clue)
(Other definitions for magisterial that I've seen before include "unlikely to be argued with" , "enforcing law" , "Commanding" .)