Permit silence in order (7)
I believe the answer is:
license
'permit' is the definition.
('license' can be a synonym of 'permit')
'silence in order' is the wordplay.
'in order' indicates an anagram (the letters in a new order).
'silence' with letters rearranged gives 'LICENSE'.
(Other definitions for license that I've seen before include "Authorise (something)" , "Give permission" , "Authorise to sell in silence" , "Authorise officially" , "Grant official permit to sell or trade" .)