Ally or companion (7)
I believe the answer is:
partner
I believe this is a double definition.
'ally' is the first definition.
(I've seen this in another clue)
'companion' is the second definition.
(I've seen this before)
(Other definitions for partner that I've seen before include "Ally" , "Business colleague" , "Colleague, bedfellow" , "Other half?" , "Spouse or business collaborator" .)