Fury shown by king over time (4)
I believe the answer is:
rage
'fury' is the definition.
(I know that fury can be written as rage)
'king over time' is the wordplay.
'king' becomes 'R' (abbreviation of Latin rex).
'over' means one lot of letters go next to another (in a down clue, some letters go over others).
'time' becomes 'age' (an age is a period of time).
'r'+'age'='RAGE'
'shown by' is the link.
(Other definitions for rage that I've seen before include "spread rapidly" , "See red" , "Uncontrollable anger" , "Latest fashion; high emotion" , "Wrath" .)