Demanding, like a monarch (6)
I believe the answer is:
asking
'demanding' is the definition.
('ask' can be a synonym of 'demand')
'like a monarch' is the wordplay.
'like' becomes 'as'.
'a monarch' becomes 'king' (king is a kind of monarch).
'as'+'king'='ASKING'
(Other definitions for asking that I've seen before include "It demands explanation!" , "Directing a question" , "Questioning" , "Inviting (to an event)" , "Demanding" .)