Main's bag makes them Scottish (5)

I believe the answer is:

pipes

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'main's' 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?

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for pipes that I've seen before include "Long tubes" , "Hollow cylindrical shapes" , "Tubes for fluids" , "Scots instrument" , "Wind instruments" .)

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

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