Understood this classic old language (6)
I believe the answer is:
gothic
'old language' is the definition.
(I've seen this before)
'understood this classic' is the wordplay.
'understood' becomes 'got' (getting is a kind of understanding).
'this classic' becomes 'hic' (I can't explain this - if you can you should believe this answer much more).
'got'+'hic'='GOTHIC'
Can you help me to learn more?
(Other definitions for gothic that I've seen before include "Style of architecture, literatureand film" , "Old-fashioned type" , "See 6 ac" , "as some Germans were" , "Building style of medieval cathedrals" .)