Changed gear in anger (4)
I believe the answer is:
rage
'anger' is the definition.
(I know that rage is a type of anger)
'changed gear' is the wordplay.
'changed' indicates an anagram.
'gear' anagrammed gives 'RAGE'.
'in' acts as a link.
(Other definitions for rage that I've seen before include "Temper - fashion" , "Fury, passion" , "Fad or anger" , "Be furious" , "Latest fashion; high emotion" .)