The cry of some wild bird (3)
I believe the answer is:
mew
'the cry' is the definition.
(mew is a kind of cry)
'of some wild bird' is the wordplay.
'of' says the answer is hidden in the clue.
'MEW' is hidden within 'some wild bird'.
(Other definitions for mew that I've seen before include "Cat's sound" , "Sound made by a cat" , "Feline sound" , "Cry of a cat or gull" , "Miaow" .)