Elvis's problems, penning extremely dreary verses (6,2,3,4)
I believe the answer is:
idylls of the king
'elvis's problems penning' is the definition.
I can't judge whether this defines the answer.
'extremely dreary verses' is the wordplay.
I cannot quite see how this works, but
'extremely' could be 'so' ('so' can mean 'extremely' or 'very') and 'so' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for idylls of the king that I've seen is " work on Arthur".)