Total prejudice ultimately knocked back some Aussie natives (4)
I believe the answer is:
emus
'aussie natives' is the definition.
Although both the answer and definition are plural nouns, I can't see how one could define the other.
'total prejudice ultimately knocked back' is the wordplay.
'total' becomes 'sum' (synonyms).
'ultimately' indicates one should take the final letters.
'knocked back' says the letters should be written backwards.
The final letter of 'prejudice' is 'e'.
'sum'+'e'='sume'
'sume' backwards is 'EMUS'.
'some' acts as a link.
Can you help me to learn more?
(Other definitions for emus that I've seen before include "Muse about flightless Australian birds" , "Large flightless birds of Australia" , "Aussie birds" , "Running birds" , "Largest native Australian birds" .)