Dictate from the dictionary (5)
I believe the answer is:
edict
'dictate' is the definition.
(thesaurus)
'from the dictionary' is the wordplay.
'from' indicates the answer is hidden within the clue.
'EDICT' is hidden within 'the dictionary'.
(Other definitions for edict that I've seen before include "Formal order" , "Cited an official proclamation" , "Canon" , "Official order" , "Injunction" .)