Duckweed reportedly forming large area across the pond (5)
I believe the answer is:
idaho
'pond' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for idaho that I've seen before include "Rocky Mountain state" , "The Gem State (US)" , "North-western state of America" , "NW state of USA" , "O, I had a change in this state" .)