Be prepared to shoot transport members (4,4)
I believe the answer is:
bear arms
'be prepared to shoot' is the definition.
(to bear arms is to carry a gun)
'transport members' is the wordplay.
'transport' becomes 'bear' (bear can mean to transport or carry).
'members' becomes 'arms' (arm is a kind of member).
'bear'+'arms'='BEAR ARMS'
(Other definitions for bear arms that I've seen before include "Serve as a soldier" , "right for American?" , "Carry weapons" , "they may be used in a tight squeeze!" , "Serve in the forces" .)