To a great extent Donne is wrong (2,3)
I believe the answer is:
no end
'to a great extent' is the definition.
(I've seen this in another clue)
'donne is wrong' is the wordplay.
'is wrong' indicates an anagram.
'donne' with letters rearranged gives 'NO END'.
(Other definitions for no end that I've seen before include "Without limit" , "Very much (slang)" , "Very much (unfinished?)" , "A lot" , "Non-stop" .)