Aerodynamically designed (5)
I believe the answer is:
sleek
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">aerodynamically designed</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sleek that I've seen before include "Aerodynamic, streamlined" , "(Of hair) smooth, glossy" , "Smooth - well-fed" , "Looking prosperous" , "with glossy coats" .)