Crossword Genius

Pith extracted from some afore­mentioned tropical plant (6)

Ross

I believe the answer is:

sesame

'tropical plant' is the definition.

'pith extracted from some aforementioned' is the wordplay.
'pith extracted from' says to hollow out the word (remove centre letters) (pith can mean the essence or heart of something).
'aforementioned' becomes 'same' ('same' can be similar in meaning to 'aforementioned').
'some' with its centre taken out is 'se'.
'se'+'same'='SESAME'

(Other definitions for sesame that I've seen before include "Open ...... is magic phrase for opening door in pantomime" , "Open ...... is magic phrase for obtaining access" , "Seeds producing an edible oil" , "Part of code for opening" , "Plant with oily seeds" .)

I've seen this clue in The Guardian.
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