Aniseed-flavored liqueur (4)
I believe the answer is:
'aniseed-flavored liqueur' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ouzo that I've seen before include "Greek aniseed-flavoured spirit" , "Strong Greek drink" , "Greek aniseed liqueur" , "Strong Greek spirit" , "booze?" .)