Lethal tempo has to stop (4)
I believe the answer is:
halt
'stop' is the definition.
(halting is a kind of stopping)
'lethal tempo has' is the wordplay.
'has' indicates the answer is hidden within the clue.
'HALT' is hidden within '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" .)