Large water lily (5)
I believe the answer is:
lotus
'large water lily' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for lotus that I've seen before include "Sacred Egyptian water lily" , "Plant that mythically induces languor" , "Mythical plant inducing languor" , "Type of water lily" , "Fruit of forgetfulness - water lily - car marque" .)