Zamenhof's language (9)
I believe the answer is:
esperanto
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">zamenhof's language</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 esperanto that I've seen before include "A language; neat prose (anag.)" , "Language invented by Dr Zamenhof" , "words, set up artificially?" , "Dr Zamenhof's language" , "Artificial speech-form" .)