Reginald (vicar?) upset church worker (6)
I believe the answer is:
verger
'church worker' is the definition.
(caretaker in a church)
'reginald vicar? upset' is the wordplay.
'reginald' becomes 'Reg' (short for Reginald).
'vicar?' becomes 'rev' (reverend).
'upset' is a reversal indicator.
'reg'+'rev'='regrev'
'regrev' back-to-front is 'VERGER'.
(Other definitions for verger that I've seen before include "Church caretaker and attendant" , "Church officer" , "Church official" .)