Kills, but Grant less cruel (9)
I believe the answer is:
strangles
'kills' is the definition.
(strangling is a kind of killing)
'grant less cruel' is the wordplay.
'cruel' is an anagram indicator.
'grant'+'less'='grantless'
'grantless' anagrammed gives 'STRANGLES'.
'but' is the link.
(Other definitions for strangles that I've seen before include "Throttles to death" , "problem for hacks?" .)