Large central computer (9)
I believe the answer is:
mainframe
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">large central computer</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 mainframe that I've seen before include "Mar famine (anag.)" , "Computer's central processing unit" , "Large central computer" , "powerful computer" , "Computer system" .)