Without interruption (5)
'without interruption' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for nonstop that I've seen before include "Ceaseless" , "done without interruption" , "Without halting" , "Ceaselessly" , "Never pausing" .)
(Other definitions for onend that I've seen before include "Continuously" , "erect" .)