Certain counties are finished with it! (3)
I believe the answer is:
sex
'it' is the definition.
('it' is a common euphemism for sex)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for sex that I've seen before include "Male or female" , "This symbol is epitome of glamour" , "Hanky-panky" , "VI (Lat.); m. or f." , "Gender" .)