Order used in some dictionaries (5)
I believe the answer is:
edict
'order' is the definition.
(synonyms)
'in some dictionaries' is the wordplay.
'in' indicates a hidden word.
'EDICT' can be found hidden inside 'some dictionaries'.
'used' is the link.
(Other definitions for edict that I've seen before include "Order issued by an authority" , "An official command" , "Cited (anag) - proclamation" , "Decree, fiat" , "Cited an official proclamation" .)