Planes (8)
I believe the answer is:
aircraft
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">planes</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for aircraft that I've seen before include "Aeroplane, helicopter etc" , "Flying machine" , "I cart RAF? (Anag)" , "Flying vehicle" , "Flying machines" .)