Dim zero's about to go for seconds (4)

I believe the answer is:

dusk

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'dim' is the definition.
(thesaurus)

I cannot understand how the rest of the clue works.

(Other definitions for dusk that I've seen before include "Time towards the end of the day" , "The darker stage of twilight" , "Gloaming" , "Nightfall" , "Period after sunset" .)

I've seen this clue in The Telegraph.

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