Foreigners (6)
I believe the answer is:
aliens
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">foreigners</span>' is the definition.<br/ ><span class="explanation-format__explanation">('alien' can be a synonym of 'foreigner')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for aliens that I've seen before include "Beings from another planet" , "Foreigners or extraterrestrials" , "Non-nationals - perhaps from Mars?" , "Outsiders" , "Forms of life assumed to exist outside Earth" .)