Bands upsetting priests (7)
I believe the answer is:
stripes
'bands' is the definition.
('stripe' can be a synonym of 'band')
'upsetting priests' is the wordplay.
'upsetting' is an anagram indicator.
'priests' anagrammed gives 'STRIPES'.
(Other definitions for stripes that I've seen before include "As standard feature" , "Insignia of rank" , "They are given to corporal" , "See 17" , "Bands of contrasting colours" .)