Chelmsford’s county (5)
I believe the answer is:
essex
'chelmsford's county' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for essex that I've seen before include "East coast county" , "County, its tasteless moneyed Man" , "Home county" , "Queen's favourite" , "Southend's county" .)