In court, she's defensive (6)

I believe the answer is:

portia

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

'in' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see a link between them that I can't see?

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

Can you help me to learn more?

(Other definitions for portia that I've seen before include "A Shakespearean heroine" , "Heroine of Shakespeare's ''The Merchant of Venice''" , "She judged Shylock (M. of V.)" , "Shakespearian legal eagle" , "Heiress of The Merchant of Venice" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.