Wading bird with long legs (5)
'wading bird with long legs' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for heron that I've seen before include "Grey or white long-legged wading bird" , "Wading bird with long neck and legs" , "Big bird" , "flier" , "Rhone (anag) - bird" .)
(Other definitions for ibis that I've seen before include "Large wader" , "Wading bird sacred to the Egyptians" , "Bird worshipped in Ancient Egypt" , "Wading bird of tropical waters" , "I'm faced with big bill" .)