Shakespeare nasty about Romeo (4)
I believe the answer is:
bard
'shakespeare' is the definition.
(I've seen this before)
'nasty about romeo' is the wordplay.
'nasty' becomes 'bad' (I can't explain this - if you can you should believe this answer much more).
'about' is an insertion indicator.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'bad' placed around 'r' is 'BARD'.
Can you help me to learn more?
(Other definitions for bard that I've seen before include "Shakespeare" , "Traditional poet" , "Animal; cruel person" , "Celtic poet" , "Gray, perhaps" .)