A name is wrongly written because of this affliction (7)
I believe the answer is:
amnesia
'written because of this affliction' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'a name is wrongly' is the wordplay.
'wrongly' is an anagram indicator.
'name'+'is'='nameis'
'nameis' anagrammed gives 'mnesia'.
'a'+'mnesia'='AMNESIA'
Can you help me to learn more?
(Other definitions for amnesia that I've seen before include "Completely forgetting" , "Failure to recall" , "illness" , "Is a name (anag.)" , "Clinical loss of memory" .)