Easing of tension (7)
I believe the answer is:
detente
'easing of tension' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for detente that I've seen before include "relaxation" , "Easing of hostility between countries" , "Easing of hostilities" , "Easing of hostility between nations" , "Easing of strained relationships between countries" .)