Crossword Genius

One practised a form of civil disobedience in compound (6)

Ross

I believe the answer is:

isatin

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

'compound' is the definition.
(I've seen this before)

'one practised a form of civil disobedience in' is the wordplay.
I cannot really see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'a' is present in the answer.
'in' is present in the answer.
The remaining letters 'st' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for isatin that I've seen before include "chemical derived from indigo" , "compound" , "Dye ingredient" .)

I've seen this clue in The Times.
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