Member - of the forces? (3)
I believe the answer is:
arm
'member' is the definition.
(member can mean a limb)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for arm that I've seen before include "inlet" , "Accoutre" , "Test of strength with elbows on the table" , "Provide with weapons" , "Shoulder-to-wrist member" .)