Centre of a wheel (3)
I believe the answer is:
hub
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">centre of a wheel</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for hub that I've seen before include "Centre of activity" , "Focal point of activity" , "Centre of wheel" , "Central part of a car wheel" , "throbbing heart" .)