Cruel people, endlessly severe in scene of battle (8)
I believe the answer is:
monsters
'cruel people endlessly severe in scene of battle' is the definition.
I can't judge whether this definition defines the answer.
'cruel people endlessly severe in' is the wordplay.
'cruel people' becomes 'mons' (I can't explain this - if you can you should give a lot more credence to this answer).
'endlessly' means to remove the last letter.
'severe' becomes 'stern' (I've seen this before).
'in' is an insertion indicator.
'stern' with its final letter taken off is 'ster'.
'mons' placed around 'ster' is 'MONSTERS'.
Can you help me to learn more?
(Other definitions for monsters that I've seen before include "Large and frightening creatures" , "Giant imaginary creatures" , "Behemoths, fiends" , "Large imaginary creatures, usually wicked" , "'Imaginary creatures, large and wicked (8)'" .)