Rule, tenet (7)
I believe the answer is:
precept
I believe this is a double definition.
'rule' is the first definition.
(I know that precept is a type of rule)
'tenet' is the second definition.
(thesaurus)
(Other definitions for precept that I've seen before include "Rubric" , "Rule of conduct or command" , "General rule for behaviour" , "Rule or principle" , "Rule of action" .)