A real mess of the title role (4)
I believe the answer is:
lear
'the title role' is the definition.
Both the definition and answer are singular nouns.
Perhaps they are linked in a way I don't understand?
'a real mess' is the wordplay.
'mess' is an anagram indicator.
'real' anagrammed gives 'LEAR'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for lear that I've seen before include "Shakespeare's tragic king (4)" , "tragic hero" , "Tragic Shakespeare king - quite real" , "See 12" , "Mad king" .)