Enduring pain south of US city (7)
I believe the answer is:
lasting
'enduring' is the definition.
('lasting' can be similar in meaning to 'enduring')
'pain south of us city' is the wordplay.
'pain' becomes 'sting' (sting is a kind of pain**).
'south of' is a charade indicator (letters next to each other).
'us city' becomes 'la'.
'sting' after 'la' is 'LASTING'.
(Other definitions for lasting that I've seen before include "long-term" , "there for long while" , "Enduring" , "Permanent" , "Abiding, durable" .)