A great many accept origin of unusual water lily
I believe the answer is:
lotus
'water lily' is the definition.
(I know this)
'a great many accept origin of unusual' is the wordplay.
'a great many' becomes 'lots' (I've seen this in another clue).
'accept' is an insertion indicator.
'origin of' suggests taking the first letters.
The first letter of 'unusual' is 'u'.
'lots' enclosing 'u' is 'LOTUS'.
(Other definitions for lotus that I've seen before include "Exotic flower" , "Sacred waterlily" , "British sports and racing car manufacturer" , "Sacred symbol" , "Type of water-lily" .)