All the confusion can be deadly (6)
I believe the answer is:
lethal
'be deadly' is the definition.
('lethal' can be a synonym of 'deadly')
'all the confusion' is the wordplay.
'confusion' indicates an anagram.
'all'+'the'='allthe'
'allthe' with letters rearranged gives 'LETHAL'.
'can' acts as a link.
(Other definitions for lethal that I've seen before include "Deadly dangerous" , "Death-dealing" , "Deadly or mortal" , "Able to cause death" , "Deadly, potentially fatal" .)