Australian bird needs bit of water held by outlaw (5,4)
I believe the answer is:
black swan
'australian bird' is the definition.
(I've seen this before)
'needs bit of water held by outlaw' is the wordplay.
'needs' becomes 'lacks' (lack is a kind of need).
'bit of' suggests taking the first letters.
'held by' means one lot of letters goes inside another.
'outlaw' becomes 'ban' (banning is a kind of outlawing).
The initial letter of 'water' is 'w'.
'lacks'+'w'='lacksw'
'lacksw' inserted into 'ban' is 'BLACK SWAN'.
(Other definitions for black swan that I've seen before include "Australian winger" , "Australian native bird" , "Aussie swimmer" , "Aquatic bird" .)