Historic British prep school (4)
I believe the answer is:
eton
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">historic british prep school</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for eton that I've seen before include "College in Berkshire" , "Famous English public school" , "Posh English school of note" , "Easy to understand" , "Posh college" .)