From Hades, guilty criminal, first bum to make unwelcome appearance (4,3,4,4)
I believe the answer is:
rear its ugly head
'bum to make unwelcome appearance' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'from hades guilty criminal' is the wordplay.
'from' becomes 'rear' (I can't explain this - if you can you should believe this answer much more).
'criminal' indicates anagramming the letters.
'hadesguilty' anagrammed gives 'itsuglyhead'.
'rear'+'itsuglyhead'='REAR ITS UGLY HEAD'
'first' acts as a link.
Can you help me to learn more?