Accepted practice (6)
I believe the answer is:
custom
'accepted practice' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for custom that I've seen before include "Traditional habit" , "''Age cannot wither her, nor ... stale (Antony and Cleopatra)" , "Usual practice" , "Traditional usage" , "Habit, usage" .)