Curiously overenthusiastic southern characters leave several holes (8)
I believe the answer is:
cavities
'holes' is the definition.
(cavity is a kind of hole)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for cavities that I've seen before include "Decayed areas in teeth" , "Is active in hollows" , "Holes (in choppers)" , "Empty spaces" .)