Zamenhof's language (9)
I believe the answer is:
esperanto
'zamenhof's language' is the definition.
(I've seen this before)
This is the entire clue.
(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" .)