Young chap upset girl over scene of assassination (6)
I believe the answer is:
dallas
'scene of assassination' is the definition.
'young chap upset girl over' is the wordplay.
'young chap' becomes 'lad' (I've seen this before).
'upset' says the letters should be written in reverse.
'girl' becomes 'sal' (feminine given name).
'over' says the letters should be written in reverse.
'lad' back-to-front is 'dal'.
'sal' reversed gives 'las'.
'dal'+'las'='DALLAS'
(Other definitions for dallas that I've seen before include "US city where JFK was assassinated" , "City in Texas; TV series" , "city built on oil" , "Texan commercial city" , "City where President Kennedy was assassinated" .)