Pond greenery (5)
I believe the answer is:
algae
'pond greenery' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for algae that I've seen before include "Plants like seaweed" , "Marine growths" , "Water plants seen in a gale" , "They grow near water and don't have ordinary roots or leaves" , "Water plants with no true stems or leaves" .)