Female of the cassowary (3)
I believe the answer is:
sow
'female' is the definition.
(female pig)
'of the cassowary' is the wordplay.
'of' indicates the answer is hidden within the clue.
'SOW' is hidden within 'cassowary'.
(Other definitions for sow that I've seen before include "Female pig" , "farm animal" , "Female badger" , "Scatter seed; pig" , "Broadcast" .)