Painstaking preparation (7)

I believe the answer is:

codeine

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'painstaking preparation' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

This is all the clue.

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(Other definitions for codeine that I've seen before include "Painkiller derived from opium" , "Pain-relieving derivative of opium" , "An anodyne" , "Common opium-based tablet used to relieve pain" , "Common painkiller" .)

I've seen this clue in The Globe and Mail.

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