Flying saucer flier (5)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">flying saucer flier</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for alien that I've seen before include "Being from another world" , "Belonging to a foreign country" , "24a [ESTRANGE]" , "repugnant" , "extraneous" .)