Repeat son's garbled, unnatural lingo (9)
I believe the answer is:
esperanto
'unnatural lingo' is the definition.
(Esperanto is a constructed language)
'repeat son's garbled' is the wordplay.
'garbled' is an anagram indicator.
'repeat'+'son'='repeatson'
'repeatson' with letters rearranged gives 'ESPERANTO'.
(Other definitions for esperanto that I've seen before include "No repeats of this artificial language, strangely" , "words, set up artificially?" , "contrived speech" , "Ape tenors (anag.)" , "Artificial international language devised in 1887" .)