Worry about badger killing (7)
I believe the answer is:
carnage
'killing' is the definition.
(carnage is a kind of killing)
'worry about badger' is the wordplay.
'worry' becomes 'care' (I've seen this before).
'about' indicates putting letters inside.
'badger' becomes 'nag' (I've seen this before).
'care' placed around 'nag' is 'CARNAGE'.
(Other definitions for carnage that I've seen before include "Killing of large numbers" , "Bloody slaughter and butchery" , "Great slaughter" , "Savage killing of people" , "Bloody slaughter as in battle" .)