Get rid of unusual alien item (9)
I believe the answer is:
eliminate
'get rid' is the definition.
(I've seen this before)
'unusual alien item' is the wordplay.
'unusual' is an anagram indicator.
'alien'+'item'='alienitem'
'alienitem' is an anagram of 'ELIMINATE'.
'of' acts as a link.
(Other definitions for eliminate that I've seen before include "Take out" , "Completely remove, get rid of" , "Wipe out" , "Do away with, get rid of" , "Exclude from further stage of competition" .)