Incestuous husband Opus Dei included after mix-up (7)
I believe the answer is:
oedipus
'mix-up' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see an association between them that I don't see?
'incestuous husband opus dei included' is the wordplay.
'opus dei' can be anagrammed to 'OEDIPUS'.
But, I'm not clear how the anagram is indicated.
'after' acts as a link.
Can you help me to learn more?
(Other definitions for oedipus that I've seen before include "Mythological king who killed his father and married his mother" , "He married his mother (and had a Freudian complex!)" , "Greek hero - complex" , "who had parental problems" , "One who married his mother" .)