Watchman who sticks to the rules? (8)
I believe the answer is:
'watchman who sticks to the rules?' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's an association between them I don't understand?
This is the entire clue.
Can you help me to learn more?
(Other definitions for observer that I've seen before include "One watching, evaluating" , "Spectator - or another weekly publication!" , "I notice" , "Looker-on" , "One watching attentively" .)