Priest upset band (6)
I believe the answer is:
stripe
'band' is the definition.
(I know that band can be written as stripe)
'priest upset' is the wordplay.
'upset' indicates an anagram.
'priest' with letters rearranged gives 'STRIPE'.
(Other definitions for stripe that I've seen before include "Priest (anag)" , "Broad band" , "Thin band of colour" , "Piece of braid indicating military rank" , "Chevron indicating rank" .)