Agreement between nations
I believe the answer is:
treaty
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">agreement between nations</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for treaty that I've seen before include "Ratified agreement between states" , "International agreement" , "alliance" , "'Pact, accord (6)'" , "Formal pact" .)