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 really understand how this works, but
'father' could be 'pa' (pa can mean dad or father) and 'pa' is located in the answer.
The remaining letters 'ter' is a valid word which might be clued in a way I don't see.
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)" .)