Councillor of state that is doubly close to emperor (6)
I believe the answer is:
'councillor of state' is the definition.
(historical type of official)
'that is doubly close to emperor' is the wordplay.
I cannot really understand how this works, but
'that is' could be 'viz' (I've seen this in another clue) and 'viz' is found within the answer.
The remaining letters 'ier' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for vizier that I've seen before include "Foreign official" , "Former Muslim official" , "Important official" , "Souped-up car" , "Muslim minister" .)