Car shaft (4)
I believe the answer is:
axle
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">car shaft</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 "revolver in one" , "A wheel revolves around it" , "Pin on which a wheel turns" , "It's pivotal" , "Rod making wheels turn" .)