Actuary upset about company reversing very firm rule (9)
I believe the answer is:
autocracy
'very firm rule' is the definition.
(rule by a dictator)
'actuary upset about company reversing' is the wordplay.
'upset' indicates anagramming the letters.
'about' indicates putting letters inside.
'company' becomes 'co' (abbreviation).
'reversing' shows that the letters should be reversed in order.
'co' back-to-front is 'oc'.
'actuary' with letters rearranged gives 'autracy'.
'autracy' placed around 'oc' is 'AUTOCRACY'.
(Other definitions for autocracy that I've seen before include "Absolute rule by an individual" , "Despotism" , "Domineering rule" , "Government by one person with absolute power" , "High-handed style" .)