The language of the organ (6)
I believe the answer is:
tongue
I believe this is a double definition.
'the language' is the first definition.
(tongue can mean a language)
'the organ' is the second definition.
(tongue is a kind of organ)
'of' acts as a link.
(Other definitions for tongue that I've seen before include "Muscular tissue in the mouth" , "Muscular organ inthe mouth" , "Part of body - language!" , "dialect" , "Part of shoe or mouth" .)