Some kangaroos terrifying bird (7)
I believe the answer is:
rooster
'bird' is the definition.
(rooster is a kind of bird)
'some kangaroos terrifying' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'ROOSTER' is hidden in the letters of 'kangaroos terrifying'.
(Other definitions for rooster that I've seen before include "Adult male domestic fowl" , "male with comb" , "Cockerel (mainly US)" , "Toreros (anag.)" , "So retro (anag.)" .)