Language operates poorly without noun (9)
I believe the answer is:
esperanto
'language' is the definition.
(Esperanto is an example)
'operates poorly without noun' is the wordplay.
'poorly' indicates anagramming the letters.
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'noun' becomes 'n'.
'operates' anagrammed gives 'esperato'.
'esperato' placed around 'n' is 'ESPERANTO'.
(Other definitions for esperanto that I've seen before include "Language invented by Dr Zamenhof" , "in which many could communicate?" , "Parse note in the artificial language" , "contrived language" , "Linguistic invention" .)