Nero's father! (5)
I believe the answer is:
pater
'nero's father' is the definition.
(I've seen this in another clue)
'father' is the wordplay.
I cannot quite understand how this works, but
'father' could be 'pa' (pa can mean dad or father) and 'pa' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for pater that I've seen before include "A posh father, from Latin" , "Our Father - . . . . . Noster" , "Taper away like father" , "Walter --, English essayist; father" , "Dad (Latin)" .)