With of. A person or thing used to achieve a purpose or intention, or to convey something. Obsolete.

A person whose actions serve to bring about a result or accomplish a purpose; an intermediate agent through whom something is done or effected…

An agent, instrument, tool, or means. With reference to a person.

figurative. A person used as a tool by another; esp. one who is employed as a decoy.

Applied to a person; cf. instrument, n. 3a, tool, n. 3.

figurative. = shoeing-horn, n. 2.