Periodically ignored fierce fury (3)
I believe the answer is:
ire
'fury' is the definition.
(ire is intense rage)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for ire that I've seen before include "Anger among admirers" , "Losing head" , "'Anger, wrath (3)'" , "passion" , "Strong feeling" .)