Sabbath, Sting, for the most part, and one of The Cars demanding the rules are observed (6)
I believe the answer is:
strict
'observed' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for strict that I've seen before include "Exacting, severe, rigid" , "Observing rules very closely" , "Requiring complete obedience" , "Excessive pride" , "Exact, rigorous" .)