Dug out of the ground and turned into fabric (5)

I believe the answer is:

denim

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

'fabric' is the definition.
(I know that denim is a type of fabric)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for denim that I've seen before include "Cloth for jeans, etc" , "Material for casual trousers or jackets" , "Tough cotton fabric" , "Coloured cotton twill" , "Fabric used for jeans" .)

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

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