Old German picked up French in the end (4)
I believe the answer is:
goth
'old german' is the definition.
(the Goths were an ancient Germanic people)
'picked up french in the end' is the wordplay.
'picked up' becomes 'got'.
'in the end' suggests the final letters.
The final letter of 'french' is 'h'.
'got'+'h'='GOTH'
(Other definitions for goth that I've seen before include "Youngster clad in black" , "Old invader" , "One of Germanic tribe that invaded Roman empire" , "Fan of gloomy music" , "Uncivilised person" .)