Centre of an amphitheatre (5)
I believe the answer is:
arena
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">centre of an amphitheatre</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 arena that I've seen before include "Wembley, for example" , "Earls Court?" , "Contest venue" , "combat zone" , "Circus ring" .)