Clean tongue (6)
I believe the answer is:
polish
I believe this clue is a double definition.
'clean' is the first definition.
(thesaurus)
'tongue' is the second definition.
(Polish is an example of a language)
(Other definitions for polish that I've seen before include "'Buff, burnish (6)'" , "class" , "See 1" , "European - gloss" , "elegance" .)