Opera about a king with followers (6)
I believe the answer is:
carmen
'opera' is the definition.
(I've seen this before)
'about a king with followers' is the wordplay.
'about' becomes 'ca' (circa).
'a king' becomes 'R' (abbreviation for rex, king in Latin).
'with' means one lot of letters go next to another.
'followers' becomes 'men' (I've seen this in other clues).
'ca'+'r'+'men'='CARMEN'
(Other definitions for carmen that I've seen before include "Bizet's great Spanish opera" , "Spanish opera by Bizet" , "Musical from Bizet opera" .)