Chief witch shortly organised mob for big sacrifice (8)
I believe the answer is:
hecatomb
'big sacrifice' is the definition.
(I've seen this before)
'chief witch shortly organised mob' is the wordplay.
I cannot really see how this works, but
an anagram of 'mob' is 'omb' which is within the answer.
This explanation may well be incorrect...
'for' acts as a link.
Can you help me to learn more?
(Other definitions for hecatomb that I've seen before include "mass slaughter" , "great public sacrifice" , "sacrifice victims" , "major sacrifice" , "Great quantity of victims" .)