Agent virtually upended into plant (4)
I believe the answer is:
iris
'plant' is the definition.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for iris that I've seen before include "Flag - flower - girl" , "Female" , "Coloured eye part" , "Fleur-de-lys" , "A flower; spirit conjured in Tempest" .)