Crime show extra, informally

PERP

Think of the shorthand term detectives use for someone they’ve just cuffed.

"Perp" is short for "perpetrator," the slang term cops and crime shows use for someone who commits a crime. The clue hints at this by calling it a "crime show extra," since perps are often the suspects or criminals featured in those stories. The "informally" part signals that the answer is a casual or abbreviated version of the full word. Think of it like how detectives on TV might say, "We’ve got the perp in custody."