Change gear in a fury (4)
I believe the answer is:
rage
'fury' is the definition.
(I know that fury can be written as rage)
'change gear' is the wordplay.
'change' indicates anagramming the letters.
'gear' is an anagram of 'RAGE'.
'in a' acts as a link.
(Other definitions for rage that I've seen before include "Gear up in violent temper" , "Uncontrollable anger" , "Latest fashion; high emotion" , "Terrible temper" , "Fury - fashion" .)