A well drilled product? (3)

I believe the answer is:

oil

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'a well' is the definition.
(oil well is a kind of well)

I can't explain the rest of the clue.

(Other definitions for oil that I've seen before include "eg Olive" , "Liquid lubricant" , "Lubricate; fuel" , "Liquid gold" , "Liquid fuel" .)

I've seen this clue in the Evening Standard.

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