Etonian's dad (5)
I believe the answer is:
pater
'etonian's dad' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pater that I've seen before include "Taper away like father" , "Walter --, English essayist; father" , "Old man" , "Our Father - . . . . . Noster" , "A posh father, from Latin" .)