Cloudy and close keeping light, almost (7)

I believe the answer is:

nebular

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'cloudy' is the definition.
(similar in meaning)

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

(Other definitions for nebular that I've seen before include "Relating to astronomical cloud" , "Misty" , "Cloudy" , "Like dust that could be stellar" , "Ran blue (anag)" .)

I've seen this clue in The Telegraph.

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