Confinement when stockpiling, having overlooked area (5-2)

I believe the answer is:

lying-in

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'confinement' is the definition.
(I know that confinement can be written as lying-in)

I don't understand the rest of the clue.

(Other definitions for lying-in that I've seen before include "Staying abed - confined in childbirth" , "Confinement" .)

I've seen this clue in The Times.

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