Airborne fighter (4)
I believe the answer is:
para
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">airborne fighter</span>' is the definition.<br/ ><span class="explanation-format__explanation">(short for paratrooper)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for para that I've seen before include "Soldier dropping to earth" , "Soldier who jumps to order? (abbr)" , "Air-drop soldier" , "Soldier (shortened)" , "soldier potentially dropped" .)