Cross about Beyeler's principal, not one framing Water Lilies (7)
I believe the answer is:
nelumbo
'cross' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for nelumbo that I've seen before include "Water lily" , "Flower" , "plant" .)