Dean carelessly includes Virginia as a US state (6)
I believe the answer is:
nevada
'a us state' is the definition.
(I've seen this before)
'dean carelessly includes virginia' is the wordplay.
'carelessly' is an anagram indicator.
'includes' indicates putting letters inside.
'virginia' becomes 'va' (US state abbreviation).
'dean' is an anagram of 'neda'.
'neda' going around 'va' is 'NEVADA'.
'as' acts as a link.
(Other definitions for nevada that I've seen before include "Curiously, Dan and Eva are in the US" , "State of western USA" , "Southwestern US state" , "South-west US state" , "See 14" .)