Crossword Genius

Bucks? A different county, we understand (5)

Ross

I believe the answer is:

harts

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'bucks?' is the definition.
The answer and definition can be both animals as well as being plural nouns.
Perhaps there's a link between them I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Another definition for harts that I've seen is " Red deer".)

I've seen this clue in The Times.
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