Bar on a car (4)
I believe the answer is:
axle
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bar on a car</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 axle that I've seen before include "Rod attachment to wheels" , "Shaft on which wheels rotate" , "wheel section" , "A wheel revolves around it" , "Rod of wheelbase" .)