Muslim official, namely one with queen (6)
I believe the answer is:
vizier
'muslim official' is the definition.
(I've seen this before)
'namely one with queen' is the wordplay.
'namely' becomes 'viz' (synonyms).
'one' becomes 'I' (Roman numeral).
'with' means one lot of letters go next to another.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'viz'+'i'+'er'='VIZIER'
(Other definitions for vizier that I've seen before include "Old Muslim official" , "Turkish bigwig" , "High official in former Ottoman Empire" , "Former Muslim official" , "High officer in various Muslim states" .)