Cassowary kin
I believe the answer is:
rhea
'cassowary kin' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rhea that I've seen before include "South American bird resembling the ostrich" , "Grounded bird" , "Moon" , "Greek goddess of fertility - running bird" , "New World flightless bird" .)