Crystalline compound I demonstrated? (6)

I believe the answer is:

isatin

'crystalline compound' is the definition.

'i demonstrated?' is the wordplay.
'demonstrated?' becomes 'satin' (as in held a sit-in, a kind of demonstration).
'i'+'satin'='ISATIN'

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

I've seen this clue in The Times.

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