Our amusement at killing (12)
I believe the answer is:
manslaughter
'killing' is the definition.
(manslaughter is a kind of killing)
'our amusement' is the wordplay.
'our' becomes 'mans' (I can't justify this - if you can you should give a lot more credence to this answer).
'amusement' becomes 'laughter' (I've seen this before).
'mans'+'laughter'='MANSLAUGHTER'
'at' is the link.
Can you help me to learn more?
(Other definitions for manslaughter that I've seen before include "Crime of killing, short of murder" , "slaying" , "charge?" , "Crime of unpremeditated killing" , "Killing without malice" .)