Wader again seen on island (4)
I believe the answer is:
ibis
'wader' is the definition.
(ibis is a kind of wader)
'again seen on island' is the wordplay.
'again' becomes 'bis' (I've seen this in other clues).
'seen on' says to put letters next to each other.
'island' becomes 'i'.
'bis' put after 'i' is 'IBIS'.
(Other definitions for ibis that I've seen before include "Bird with long neck and legs and a curved bill" , "Bird venerated by ancient Egyptians" , "Bird sacred in Ancient Egypt" , "Eastern" , "Wader once sacred in Egypt" .)