Marsh birds (6)
I believe the answer is:
egrets
'marsh birds' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for egrets that I've seen before include "waders" , "Greets in way of certain herons (" , "Kind of herons with long white feathers" , "White wading birds" , "Fliers" .)