Crossword Genius

Region monitored for auditor (5)

Ross

I believe the answer is:

tract

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'region' is the definition.
(both can mean a large piece of land)

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

Can you help me to learn more?

(Other definitions for tract that I've seen before include "Large area of land or small booklet" , "anthem" , "Extensive area of land" , "Religious treatise" , "Large area; treatise" .)

I've seen this clue in The Times.
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