Sabbath? Rubbish band! (6)
I believe the answer is:
stripe
'band' is the definition.
('stripe' can be a synonym of 'band')
'sabbath? rubbish' is the wordplay.
'sabbath?' becomes 's'.
'rubbish' becomes 'tripe' ('tripe' can be a synonym of 'rubbish').
's'+'tripe'='STRIPE'
(Other definitions for stripe that I've seen before include "Military rank indicator" , "Chevron; band" , "Band of colour - 3 of rank" , "Narrow band of colour" , "Piece of braid indicating military rank" .)