Opening chapter taken from bible, perhaps (5)

I believe the answer is:

stoma

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'opening' is the definition.
(I know that stoma is a type of opening)

I don't understand how the rest of the clue works.

(Other definitions for stoma that I've seen before include "Pore in plant" , "surgical opening" .)

I've seen this clue in The Times and The Sunday Times.

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