Crossword Genius

Self-driving car that is made to leave, leaves (4)

Ross

I believe the answer is:

herb

I'm a little stuck... Click here to teach me more about this clue!

'leave leaves' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for herb that I've seen before include "Savoury plant" , "Basil, for example, is one" , "Rosemary, for example" , "plant with useful properties" , "ingredient for recipe?" .)

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