Bulbous plant (4)
I believe the answer is:
lily
'bulbous plant' is the definition.
(lily is a kind of bulbous plant)
This is all the clue.
(Other definitions for lily that I've seen before include "Flower, maybe of the valley" , "Flower of purity" , "Tiger -; water -" , "Eg, arum, calla" , "Trumpet-shaped flowering plant" .)