In court, argue against jail in speech (10)

I believe the answer is:

quadrangle

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

'in court' is the definition.
'quadrangle' can be an answer for 'court' (thesaurus). I am not certain of the 'in' bit.

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for quadrangle that I've seen before include "Square" , "Four-sided courtyard" , "Rectangular courtyard" , "court" .)

I've seen this clue in The Guardian.

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