Change direction, ever changing (4)
'change direction' is the definition.
(I've seen this before)
'ever changing' is the wordplay.
'changing' is an anagram indicator.
'ever' is an anagram of 'VEER'.
(Other definitions for veer that I've seen before include "Change direction or course, like wind", "Deviate", "Suddenly change direction", "Sudden direction change", "Swing around".)