Ned failed translation on old English writer (6,5)
I believe the answer is:
daniel defoe
'writer' is the definition.
(I've seen this before)
'ned failed translation on old english' is the wordplay.
'translation' is an anagram indicator.
'on' is a charade indicator (letters next to each other).
'old english' becomes 'oe'.
'ned'+'failed'='nedfailed'
'nedfailed' with letters rearranged gives 'danieldef'.
'danieldef'+'oe'='DANIEL DEFOE'
(Other definitions for daniel defoe that I've seen before include "Novelist" , "Moll Flanders writer" , "Author" .)