English county and a Midwest US state (4)

I believe the answer is:

iowa

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'midwest us state' is the definition.
(I've seen this before)

'english county and a' is the wordplay.
'english county' becomes 'iow' (I can't explain this - if you can you should give a lot more credence to this answer).
'and' is a charade indicator (letters next to each other).
'iow'+'a'='IOWA'

Can you help me to learn more?

(Other definitions for iowa that I've seen before include "'Hawkeye State'" , "State of USA" , "US state, capital Des Moines" , "Central US state" , "US state, three vowels" .)

I've seen this clue in The Telegraph.

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