Where Paris was once, without end or beginning (5)
I believe the answer is:
intro
This could be a double definition.
'where paris was once without end' is the first definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'beginning' is the second definition.
(short for introduction)
'or' acts as a link.
(Other definitions for intro that I've seen before include "Opening passage (of music) (colloq.)" , "Beginning (colloq.)" , "Beginning (informal)" , "Opening instrumental passage of song" , "Preliminary part" .)