In a Commercial Crime policy, a "messenger" is defined as:

The definition of a "messenger" in a Commercial Crime policy pertains to individuals responsible for the care and custody of insured property when it is located outside the premises. The correct answer identifies a messenger as the insured, a relative of the insured, a business partner, or an employee who has the responsibility of safeguarding insured property while it is outside of the business's physical location.

This designation is crucial in insurance as it clarifies who is recognized under the policy to be responsible for the property during transport or when outside of the premises, thus ensuring proper coverage and protection against loss or theft during those times. This understanding aligns with the purpose of Commercial Crime policies, which aim to provide coverage against specific risks associated with crime that could impact the business when its property is not secured within its own premises.

The other possible definitions do not accurately capture the scope of "messenger" as specified in the policy. For instance, some options focus only on the care and custody within the premises or imply limitations that contradict the established definitions within the insurance context. Therefore, recognizing the unique role and responsibilities of a messenger as defined in answer C is essential for understanding the coverage and protection provided by a Commercial Crime policy.