Graduate gets to grips with institute and the majority briefly from plant (6)

I believe the answer is:

mimosa

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'plant' is the definition.
(mimosa is a kind of plant)

I don't understand the rest of the clue.

(Other definitions for mimosa that I've seen before include "Tropical plant" , "Plant genus popularly extended to the Acacia" , "Sensitive plant genus; so maim (anag.)" , "Australian 15 across" , "So maim with tropical shrub bearing fragrant flowers" .)

I've seen this clue in the Irish Times (Crosaire) and the Irish Times.

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