The language of numbers (6)
I believe the answer is:
arabic
'the language' is the definition.
(Arabic is a language)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for arabic that I've seen before include "CIA bar on this Middle East language" , "Semitic language" , "1 [GCSE]" , "Official language of Egypt" , "Language (of numbers)" .)