On the same side (6)
I believe the answer is:
allied
'on the same side' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for allied that I've seen before include "Joined by treaty or agreement" , "Joined in friendship, treaty, etc" , "Joined together for mutual support" , "Joined to, combined with" , "Joined together for a purpose" .)