Propriety (9)
There are a few possibilities for this:
rightness
'propriety' is the definition.
(I know that decorum is a type of propriety)
This is the entire clue.
(Other definitions for decorum that I've seen before include "modesty" , "Proper form" , "(Of outward appearances) what is proper" , "Correctness or dignity of behaviour" , "Dignity of behaviour or procedure" .)
'propriety' is the definition.
(I know that decency is a type of propriety)
This is the entire clue.
(Other definitions for decency that I've seen before include "respectful behaviour" , "Seemliness" , "Decorum" , "Respectable behaviour" , "Good taste; integrity" .)
'propriety' is the definition.
(I know that rightness is a type of propriety)
This is all the clue.
(Another definition for rightness that I've seen is " A condition of morality".)