Language a scholar finally understood (5)
I believe the answer is:
argot
'language' is the definition.
(argot can mean jargon or slang)
'a scholar finally understood' is the wordplay.
'finally' indicates one should take the final letters.
'understood' becomes 'got' (getting is a kind of understanding).
The final letter of 'scholar' is 'r'.
'a'+'r'+'got'='ARGOT'
(Other definitions for argot that I've seen before include "Particular group's jargon" , "Cant" , "Jargon - patois" , "Language of a particular group" , "Patois, vernacular" .)