Person at end of line misconstrued language (9)
I believe the answer is:
esperanto
'language' is the definition.
(Esperanto is an example)
'person at end of line misconstrued' is the wordplay.
'end of' suggests the final letters.
'misconstrued' indicates an anagram.
The final letter of 'line' is 'e'.
'person'+'at'+'e'='personate'
'personate' anagrammed gives 'ESPERANTO'.
(Other definitions for esperanto that I've seen before include "composite language" , "artificial tongue" , "Parse note in the artificial language" , "largely unknown language" , "common language" .)