Imposed order or decree (6)
I believe the answer is:
diktat
This clue is a double definition.
'imposed order' is the first definition.
(I've seen this before)
'decree' is the second definition.
(I've seen this before)
(Other definitions for diktat that I've seen before include "Harsh order or decree" , "Undemocratic decree" , "Forceful order that must be obeyed" , "A firm statement or decree" , "An order that allows no opposition" .)