Crossword Genius

We abandoned hydrogen plant (4)

Ross

I believe the answer is:

iris

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'plant' is the definition.
(type of flower)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for iris that I've seen before include "Fleur-de-lys" , "Pupil is at the centre of this" , "Lily" , "One controlling pupil' s reactions" , "Pupil's place?" .)

I've seen this clue in The Irish Times.
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