Australian natives given OK to return, unfortunately (6)
I believe the answer is:
koalas
'australian natives' is the definition.
(I know that koalas are native to Australia)
'given ok to return unfortunately' is the wordplay.
'given' means one lot of letters go next to another.
'to return' says the letters should be written in reverse.
'unfortunately' becomes 'alas' ('alas' is used to express regret).
'ok' back-to-front is 'ko'.
'ko' next to 'alas' is 'KOALAS'.
(Other definitions for koalas that I've seen before include "Australian arboreal marsupials" , "Tree-climbing marsupials in Australia" , "Cute animals" , "Tailless Australian marsupials" , "Australian tree-climbing bears" .)