Former county (4)
'former county' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for avon that I've seen before include "Former English county" , "River running through Bath" , "[WILTS] flower" , "Bath's river" , "Casual attitude" .)
'former county' is the definition.
(I know that Middlesex is a former county)
This is all the clue.
(Other definitions for middlesex that I've seen before include "Cricketers" , "Cricketing county" .)