Pact, accord (6)
I believe the answer is:
treaty
This clue is a double definition.
'pact' is the first definition.
(synonyms)
'accord' is the second definition.
(synonyms)
(Other definitions for treaty that I've seen before include "Formal pact" , "alliance" , "Pact or agreement between nations" , "Formal agreement between states" , "Pact, accord between states" .)