It's used for shooting - America would be reformed without one! (6)
I believe the answer is:
camera
'it's used for shooting america would' is the definition.
I can't judge whether this defines the answer.
'reformed without one' is the wordplay.
'reformed' becomes 'cara' (I can't justify this - if you can you should believe this answer much more).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'one' becomes 'me' (a setter might use 'one' to humourously mean 'me').
'cara' going around 'me' is 'CAMERA'.
'be' acts as a link.
Can you help me to learn more?
(Other definitions for camera that I've seen before include "Still producer" , "Light-proof box with a lens and film" , "A court held in it is not open to the public" , "Snapper's kit" , "one that produces pictures" .)