Measure the crack the rain’s come through (4)

I believe the answer is:

acre

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'measure' is the definition.
(acre is a kind of measure)

I cannot understand how the remainder of the clue works.

(Other definitions for acre that I've seen before include "0.405 of a hectare" , "Imperial unit of area" , "Unit of land area" , "Unit of land measurement" , "amount of land" .)

I've seen this clue in the Evening Standard.

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