Long-legged wading bird (6)
(Other definitions for egret that I've seen before include "Kind of white heron - greet it" , "Heron-like wader" , "Mainly white heron" , "Wading bird like a heron" , "Stork-like bird" .)
'long-legged wading bird' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for heron that I've seen before include "One bird" , "Tall wading bird" , "Wader" , "Rhone (anag) - bird" , "Graceful grey bird with long neck" .)
(Other definitions for avocet that I've seen before include "Curved-bill shore bird" , "Black and white Eurasian long-legged wading bird" , "Long-legged wader" , "Black-and-white shorebird with upward-curving bill" , "Shorebird with bill curving upwards" .)