Crossword Genius

Mechanical part in wristwatch or car? (6,4)

Ross

I believe the answer is:

second gear

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

'car?' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I can't see?

'mechanical part in wristwatch' is the wordplay.
I cannot quite see how this works, but
'part' could be 'ear' (ear is a kind of part) and 'ear' is located in the answer.
This explanation may well be incorrect...

'or' is the link.

Can you help me to learn more?

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