Bores with raw material (4)

I believe the answer is:

ores

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

'raw material' is the definition.
(I've seen this in another clue)

'bores with' is the wordplay.
'ORES' is hidden within the letters.
But, I am unsure how this is indicated.

Can you help me to learn more?

(Other definitions for ores that I've seen before include "Mined minerals" , "Sources of metal" , "Bauxite, haematite etc" , "Mineral deposits" , "Metal-bearing minerals" .)

I've seen this clue in The Mirror.

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