Memory loss means I misplaced article (7)
I believe the answer is:
amnesia
'memory loss' is the definition.
(synonyms)
'means i misplaced article' is the wordplay.
'misplaced' is an anagram indicator (letters in the wrong places).
'article' becomes 'a' (the indefinite article in English).
'means'+'i'='meansi'
'meansi' is an anagram of 'amnesi'.
'amnesi'+'a'='AMNESIA'
(Other definitions for amnesia that I've seen before include "Recall trouble" , "Complaint" , "As a mine (anag)" , "Am I sane? (anag)" , "Is a name (anag.)" .)