In home counties these days, smallest part unsullied (4-5)
I believe the answer is:
snow-white
'unsullied' is the definition.
'in home counties these days smallest part' is the wordplay.
'in' means one lot of letters goes inside another.
'home counties' becomes 'se' (Home Counties in the South East of England).
'these days' becomes 'now' (I've seen this in another clue).
'smallest part' becomes 'whit' (a very small part or amount).
'now'+'whit'='nowwhit'
'se' going around 'nowwhit' is 'SNOW-WHITE'.
(Other definitions for snow-white that I've seen before include "Seven dwarfs heroine" , "Friend of seven dwarfs" , "Perfectly pure -- fairytale heroine" , "Disney's first full-length film" , "Completely pure - fairytale heroine" .)