Go to fight hairy members (4,4)
I believe the answer is:
bear arms
'go to fight' is the definition.
(take up arms for battle)
'hairy members' is the wordplay.
'hairy' becomes 'bear' (I can't explain this - if you can you should believe this answer much more).
'members' becomes 'arms' (arm is a kind of member).
'bear'+'arms'='BEAR ARMS'
Can you help me to learn more?
(Other definitions for bear arms that I've seen before include "Serve in the forces" , "Serve as a soldier" , "they may be used in a tight squeeze!" , "Carry weapons" , "right for American?" .)