Close to neverending darkness (4)

I believe the answer is:

nigh

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'close to' is the definition.
(I've seen this in another clue)

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

(Other definitions for nigh that I've seen before include "Near; close" , "Near (old use)" , "Near (poetic)" , "Adjacent" , "See 23" .)

I've seen this clue in The Sun.

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