Gelatine is in tumbler (9)

I believe the answer is:

isinglass

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

'is in tumbler' is the wordplay.
'tumbler' becomes 'glass' (I've seen this before).
'is'+'in'+'glass'='ISINGLASS'

(Other definitions for isinglass that I've seen before include "What's got from fish" , "Fish gelatin" , "One transparent material" , "Gelatine" , "Some Muscovite" .)

I've seen this clue in The Telegraph.

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