Treatment centre (6)
I believe the answer is:
clinic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">treatment centre</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for clinic that I've seen before include "Place for specialised treatment, from doctor or politician" , "Building where outpatients are treated" , "Which outpatients attend" , "Place offering treatment" , "Healthcare facility" .)