Riddonkulous

Five to start: a small furry animal, one that often gives people a startle as it scurries by, so keep the cat nearby. The last four are a way to snare something, maybe even the first. Add en to this four and it becomes an illegal police trick. Combine the five and the four and you have a device people still try to make a better version of. When it works well, it uses the last four on the first five.