The figure of speech that uses a related attribute for a thing, as “the crown” for the monarchy, is metonymy.
Metonymy works by replacing a word with another term that is closely associated with it. “The crown” can stand for a monarch or the institution of monarchy; “the White House” can refer to the U.S. president or administration; and “the bench” can refer to judges. The relationship is conceptual or cultural rather than based on physical resemblance.
Metonymy appears constantly in journalism, politics, literature, and everyday speech. It allows writers to compress a complicated institution, group, or idea into a vivid concrete image. In “the pen is mightier than the sword,” the pen represents writing or intellectual influence, while the sword represents military force. These substitutions work because readers recognize the established association.
Metonymy is often confused with metaphor and synecdoche. A metaphor compares unlike things by resemblance, while metonymy substitutes one associated thing for another. Synecdoche is a narrower related device in which a part represents the whole, or the whole represents a part, such as “hands” for workers. Because “the crown” is associated with monarchy but is not a literal part standing for the whole, metonymy is the canonical answer.