End of round Fury fell (4)
I believe the answer is:
dire
'fell' is the definition.
(thesaurus)
'end of round fury' is the wordplay.
'end of' indicates one should take the final letters.
'fury' becomes 'ire' (ire is intense rage).
The last letter of 'round' is 'd'.
'd'+'ire'='DIRE'
(Other definitions for dire that I've seen before include "Frightful" , "Dreadful; grim" , "Appalling or extreme" , "'Dreadful, awful (4)'" , "Extremely serious or urgent" .)