Plain folk from the south irked, note, with everyone (8)
I believe the answer is:
llaneros
'plain folk' is the definition.
(people living on a plain or llano)
'from the south irked note with everyone' is the wordplay.
'from the south' shows that the letters should be reversed in order (in a down clue, letters go up).
'irked' becomes 'sore' (I've seen this in another clue).
'note' becomes 'n' (abbreviation).
'with' is a charade indicator (letters next to each other).
'everyone' becomes 'all' (all people).
'sore'+'n'+'all'='sorenall'
'sorenall' back-to-front is 'LLANEROS'.
(Another definition for llaneros that I've seen is " plain people".)