Crossword Genius

A worn machine part (3)

Ross

I believe the answer is:

mac

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This might be a double definition.

'a worn machine' is the first definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?

'part' is the second 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 don't see?

Can you help me to learn more?

(Other definitions for mac that I've seen before include "Raincoat (colloq.)" , "Waterproof coat (colloq.)" , "Waterproof raincoat, in short" , "Coat - computer" , "laptop?" .)

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