Relaxing of tension (7)
I believe the answer is:
detente
'relaxing of tension' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for detente that I've seen before include "Easing of hostility between nations" , "Easing of international tension" , "Easing of strained relations" , "The easing of tensions between nations" , "peace during hostilities" .)