Big name in car rentals (4)
I believe the answer is:
avis
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">big name in car rentals</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 avis that I've seen before include "Unusual bird or extraordinary person - rara ?." , "Rara --, rare bird (or car rental firm)" .)