Crossword Genius

Caffeine, say — help keeping all OK, if stimulated (8)

Ross

I believe the answer is:

alkaloid

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'caffeine say' is the definition.
(caffeine is a kind of alkaloid)

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for alkaloid that I've seen before include "Plant compound having physiological effect on humans" , "Organic compound with toxic or medicinal property" , "Organic compound having physiological action" , "Any of a group of nitrogenous basic compounds found in plants" .)

I've seen this clue in The Times.
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