Lethal tempo has to stop (4)
I believe the answer is:
halt
'stop' is the definition.
(halt can mean to stop)
'lethal tempo has' is the wordplay.
'has' indicates a hidden word.
'HALT' is hidden in the letters of 'lethal tempo'.
'to' is the link.
(Other definitions for halt that I've seen before include "Falter - stop" , "Stop; minor station" , "Stop or pause" , "Bring to a stop; lame" , "game" .)