Usually not. This is a very common accidental injury at all ages, even in the process of getting born. It's not the typical injury inflicted by an abuser.
Fractured clavicle. It can be due to child abuse, but this is one of the fractures that is not uncommonly seen after birth, particularly in a large baby with a difficult labor. In general, when seen in isolation it is probably not due to child abuse.
No. The clavicle (collar bone) is the most commonly fractured bone in the body. Typically it breaks following a fall on an outstretched arm. Simply being fractured is not a sign of child abuse, but repeated injuries or a history inconsistent with the injury may suggest either abuse or even an underlying metabolic problem. A concern of abuse should be directed to local authority or an abuse hotline.