Outside parties held back by force in extremely dark time (8)

I believe the answer is:

midnight

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'time' is the definition.
(midnight is a kind of time)

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

(Other definitions for midnight that I've seen before include "when PM finishes" , "Possible time for feast" , "-- Sun; -- blue" , "When PM turns to AM" , "type of oil burnt by late work" .)

I've seen this clue in The Guardian.

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