Crossword Genius

Two things eyewitness does with a timer (9)

Ross

I believe the answer is:

stopwatch

I'm a little stuck... Click here to teach me more about this clue!

'timer' is the definition.
(I know that stopwatch is a type of timer)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for stopwatch that I've seen before include "Timepiece used in racing" , "Timing device, for sports perhaps" , "instrument" , "Timer for races, etc" , "Timepiece for recording speed of racers" .)

I've seen this clue in the Sydney Morning Herald.
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