Obscures one source of malpractice in English county (6)
I believe the answer is:
bedims
'obscures' is the definition.
('bedim' can be a synonym of 'obscure')
'one source of malpractice in english county' is the wordplay.
'one' becomes 'i' (Roman numeral).
'source of' says to take the initial letters.
'in' means one lot of letters goes inside another.
'english county' becomes 'Beds' (abbreviation for Bedfordshire).
The first letter of 'malpractice' is 'm'.
'i'+'m'='im'
'im' going within 'beds' is 'BEDIMS'.
(Another definition for bedims that I've seen is " Blears".)