Killed a large number (4)
I believe the answer is:
slew
This clue is a double definition.
'killed' is the first definition.
(historical past tense of slay)
'a large number' is the second definition.
(slew can mean a large amount of something)
(Other definitions for slew that I've seen before include "a large number in America" , "a great number in Chicago" , "twisted position" , "Change direction abruptly" , "Turn uncontrollably" .)