Maybe simple Appalachian horse: one's going to charge Yankee (9)

I believe the answer is:

hillbilly

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'maybe simple appalachian' is the definition.
I can't judge whether this definition defines the answer.

'horse one's going to charge yankee' is the wordplay.
'horse' becomes 'H' (abbreviation as in horse power).
'one' becomes 'i' (Roman numeral).
'going to' becomes 'll' (as in he'll, we'll etc).
'charge' becomes 'bill' (synonyms).
'yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'h'+'i'+'ll'+'bill'+'y'='HILLBILLY'

Can you help me to learn more?

(Other definitions for hillbilly that I've seen before include "US rustic" , "Rustic American" , "Country-and-western music" , "Unsophisticated person from the backwoods of America" , "Unsophisticated person - country music" .)

I've seen this clue in The Times.

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