When one’s ticker stops, one expires (9)
I believe the answer is:
stopwatch
But I can't explain it at all! Could you help me understand?
(Other definitions for stopwatch that I've seen before include "Timepiece for exact timing" , "Timing device, for sports perhaps" , "Race timer" , "Timepiece for recording speed of racers" , "Timepiece for timing, a race perhaps" .)