Order used in the dictionary (5)
I believe the answer is:
edict
'order' is the definition.
(synonyms)
'in the dictionary' is the wordplay.
'in' says the answer is hidden in the clue.
'EDICT' is hidden in the letters of 'the dictionary'.
'used' acts as a link.
(Other definitions for edict that I've seen before include "Legally binding proclamation" , "Formal proclamation" , "Decree, order" , "Formal order" , "Regulation" .)