Some move erratically to change course (4)
I believe the answer is:
veer
'change course' is the definition.
(thesaurus)
'some move erratically to' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'VEER' is hidden in the letters of 'move erratically to'.
(Other definitions for veer that I've seen before include "Deviate" , "Suddenly change direction" , "Swing around" , "Change direction sharply" , "Change direction or course, like wind" .)