Head of state's icon, working with charm (9)
I believe the answer is:
monarchic
'head of state's' is the definition.
Both the answer and definition are adjectives. Maybe there's an association between them I don't understand?
'icon working with charm' is the wordplay.
'working with' indicates anagramming the letters (working with the letters).
'icon' with its letters anagrammed with 'charm' gives 'MONARCHIC'.
(Other definitions for monarchic that I've seen before include "Like top person" , "Sovereign's" , "from a sovereign" , "of head of state" .)