Some French chief returning, in charge and authoritarian (8)
I believe the answer is:
despotic
'authoritarian' is the definition.
('despotic' can be a synonym of 'authoritarian')
'some french chief returning in charge' is the wordplay.
'some french' becomes 'des'.
'chief' becomes 'top' ('top' can be a synonym of 'chief'**).
'returning' says the letters should be written backwards.
'in charge' becomes 'ic'.
'top' in reverse letter order is 'pot'.
'des'+'pot'+'ic'='DESPOTIC'
'and' acts as a link.
(Other definitions for despotic that I've seen before include "Like a cruel ruler" , "'Cruel and oppressive, as a dictator (8)'" , "Exercising absolute power" , "Referring to absolute power" , "of tyrant" .)