Aussie native behind tailless bird (7)
I believe the answer is:
rooster
'bird' is the definition.
(I know that rooster is a bird)
'aussie native behind tailless' is the wordplay.
'aussie native' becomes 'roo' (short for kangaroo).
'behind' becomes 'stern' (the back or behind of a ship).
'tailless' means to remove the last letter (the tail of the word is removed).
'stern' with its final letter taken away is 'ster'.
'roo'+'ster'='ROOSTER'
(Other definitions for rooster that I've seen before include "Adult male chicken" , "Male domestic fowl (US)" , "Chanticleer" , "Toreros (anag.)" , "One crows" .)