Strange, alien (7)
I believe the answer is:
unknown
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">strange</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that strange can be written as unknown)</span><br/ ><br/ >'<span class="explanation-format__original">alien</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that alien can be written as unknown)</span><br/ ><br/ ></span>
(Other definitions for unknown that I've seen before include "Strange - obscure" , "Mysterious" , "Unidentified - not explored" , "anon?" , "Not recognised by anyone" .)