Former English county (4)
I believe the answer is:
avon
'former english county' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for avon that I've seen before include "River of the Bard" , "Shakespeare was known as the Bard of . . . ." , "English river flowing through Stratford" , "Casual attitude" , "Name of several English rivers" .)