Shirt feature (6)
(Other definitions for arm that I've seen before include "Upper limb" , "Limb or branch" , "Equip with a limb" , "Activate fuse" , "Shoulder-to-wrist member" .)
(Other definitions for collar that I've seen before include "Neckband of shirt" , "Apprehend (someone)" , "Arrest (sl.)" , "Appropriate - piece of neckwear" , "Grab by the neckband?" .)