Well lit line travelling all the way down into big city every evening (7)
I believe the answer is:
nightly
'every evening' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for nightly that I've seen before include "When owls fly" , "when Casanova in action?" , "Happening every evening" , "Regularly during the hours of darkness" , "Every day between sunset and sunrise" .)