Ill-will apparent when madmen start yelling about it (6)
I believe the answer is:
enmity
'ill-will' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for enmity that I've seen before include "Hostility, bad feeling towards" , "Personal hostility" , "ill will" , "Hostility between opposing people or countries" , "Hostility, ill-will" .)