Partners in war (6)
I believe the answer is:
allies
'partners in war' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for allies that I've seen before include "They support and encourage each other" , "Mutual supporters, like countries through treaty" , "Countries that opposed Hitler" , "Formally cooperating countries" , "They help each other, confederates" .)