Lots upset after vicar renounces allegiance (7)
I believe the answer is:
revolts
'renounces allegiance' is the definition.
(revolting is a kind of renouncing allegiance)
'lots upset after vicar' is the wordplay.
'upset' indicates an anagram.
'after' is a charade indicator (letters next to each other).
'vicar' becomes 'rev' (short for reverend).
'lots' anagrammed gives 'olts'.
'olts' put after 'rev' is 'REVOLTS'.
(Other definitions for revolts that I've seen before include "Rebels" , "Acts of defiance" , "Disgusts" .)