Some kangaroos terrify a bird (7)
I believe the answer is:
rooster
'bird' is the definition.
(I know that rooster is a poultry)
'some kangaroos terrify a' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'ROOSTER' can be found hidden inside 'kangaroos terrify a'.
(Other definitions for rooster that I've seen before include "Bird that wakes up" , "Cockerel (mainly US)" , "8 [RURAL] alarm call" , "One may crow" , "Crowing bird" .)