Airborne trooper (4)
I believe the answer is:
para
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">airborne trooper</span>' is the definition.<br/ ><span class="explanation-format__explanation">(abbreviation of paratrooper)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for para that I've seen before include "Soldier that jumps from planes" , "soldier potentially dropped" , "Soldier who jumps to order? (abbr)" , "High-jumper" , "Soldier who's dropped in? (abbr)" .)