Nile wader
I believe the answer is:
'nile wader' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ibis that I've seen before include "Near-colourless mineral" , "I'm faced with big bill" , "Bird, sacred to ancient Egyptians" , "Sacred Egyptian bird" , "Bird sacred in Ancient Egypt" .)