That's an order! (5)
There are a few possibilities for this:
directive
'that's an order' is the definition.
(order of classical architecture)
This is the entire clue.
(Other definitions for ionic that I've seen before include "Sort of column" , "Like some Greek architecture" , "Greek order" , "Order for architects" , "Relating to charged particles" .)
'that's an order' is the definition.
(synonyms)
This is all the clue.
(Other definitions for edict that I've seen before include "Canon" , "Formal announcement" , "An official command" , "Order issued by an authority" , "Decree, order" .)
'that's an order' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for directive that I've seen before include "Official instruction" , "order" , "command" .)