Many people care about wholesale slaughter (8)
I believe the answer is:
massacre
'wholesale slaughter' is the definition.
(I've seen this before)
'many people care about' is the wordplay.
'many people' becomes 'mass'.
'about' indicates an anagram.
'care' with letters rearranged gives 'acre'.
'mass'+'acre'='MASSACRE'
(Other definitions for massacre that I've seen before include "Overwhelming defeat" , "Murder (of many persons)" , "Slaughter of large number of people" , "Slaughter, pogrom" , "Destroy" .)