Lit up a plant (3)

I believe the answer is:

til

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'a plant' is the definition.
Both the definition and answer are singular nouns.
Maybe there's an association between them I don't understand?

'lit up' is the wordplay.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'lit' back-to-front is 'TIL'.

Can you help me to learn more?

(Another definition for til that I've seen is " Sesame".)

I've seen this clue in the Sydney Morning Herald.

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