Depart from capital of Ecuador, stopping early (4)
I believe the answer is:
quit
'depart from' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for quit that I've seen before include "Stop; abandon" , "Leave (one's job)" , "Desist" , "Leave office" , "Leave or abandon" .)