Demon, I suspect, royal bully (8)
I believe the answer is:
domineer
'bully' is the definition.
(I know that bully is the is a more specific form of the action of domineer.)
'demon i suspect royal' is the wordplay.
'suspect' indicates anagramming the letters (a suspicious or unusual spelling).
'royal' becomes 'er' (abbreviation for Elizabeth Regina).
'demon'+'i'='demoni'
'demoni' is an anagram of 'domine'.
'domine'+'er'='DOMINEER'
(Other definitions for domineer that I've seen before include "Behave imperiously" , "Ride roughshod over" , "behave arrogantly" , "Ore mined badly could tend to overbear" , "Tyrrannise" .)