Cry of the sea-hawk (3)
I believe the answer is:
aha
'cry' is the definition.
(I have seen 'Cry of triumph ' mean 'aha' so perhaps 'cry' could also mean 'aha')
'of the sea-hawk' is the wordplay.
'of' indicates the answer is hidden within the clue.
'AHA' is hidden within 'sea hawk'.
(Other definitions for aha that I've seen before include "Triumphant cry" , "Cry of triumph" , "Exclamation of triumph or mockery, a palindrome" , "Cry of surprise" , "Surprised expression" .)