Madness of King over time (4)
I believe the answer is:
rage
'madness' is the definition.
('rage' can be a synonym of 'madness')
'king over time' is the wordplay.
'king' becomes 'r' (r is abbreviation for rex).
'over' says to put letters next to each other.
'time' becomes 'age' (age is a kind of time**).
'r'+'age'='RAGE'
'of' is the link.
(Other definitions for rage that I've seen before include "Gear up in violent temper" , "Violent anger, maybe on road" , "High dudgeon" , "Uncontrolled anger" , "Wrath" .)