Deadline that wouldn't mean a lot to a low fellow (6)

I believe the answer is:

curfew

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'deadline' is the definition.
(curfew is a kind of deadline)

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

(Other definitions for curfew that I've seen before include "When people were housebound" , "Regulation requiring people to be indoors during certain hours" , "Restriction on night-time movements" , "Order restricting time not at home" , "Early closing time imposed by military" .)

I've seen this clue in the Evening Standard.

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