Claudius’s successor (4)
I believe the answer is:
nero
'claudius's successor' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nero that I've seen before include "Emperor who played the fiddle" , "Roman emperor infamous for his cruelty" , "Emperor said to have started the fire that destroyed Rome" , "Roman Emperor, 54-68 AD" , "He's reported to have fiddled while Rome burned" .)