Land where religions clashed (4)

I believe the answer is:

acre

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'land' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for acre that I've seen before include "Muslims here besieged" , "Care about the piece of land" , "A state of W Brazil" , "Persistent tendency" , "Unit of land measurement" .)

I've seen this clue in The Sun.

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