Great Swiss mathematician (5)
I believe the answer is:
euler
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">great swiss mathematician</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for euler that I've seen before include "Noted blind Swiss mathematician" , "calculating foreigner" , "Swiss mathematician; sounds like lubricator" , "Swiss scientist" , "Leonhard -----, founder of mathematical analysis" .)