Chuck, a supporter (5)
I believe the answer is:
sling
I believe this is a double definition.
'chuck' is the first definition.
(chuck means throw as does sling)
'a supporter' is the second definition.
(a sling supports an injured arm)
(Other definitions for sling that I've seen before include "Stone-throwing weapon" , "American drink" , "Arm bandage; hurl" , "Injured-arm support" , "attached to a rifle, perhaps" .)