Hertfordshire cathedral city (2,6)
I believe the answer is:
st albans
'hertfordshire cathedral city' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for st albans that I've seen before include "English city" , "Modern Verulamium" , "Cathedral city north of London" , "The Roman Verulamium" , "Hertfordshire cathedral city" .)