Complete change of direction (1-4)
I believe the answer is:
u-turn
'complete change of direction' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for u-turn that I've seen before include "Sharp reversal of direction" , "Complete reverse of car or attitude" , "Sudden complete change of plan" , "A complete reverse of direction" , "180 degrees change of direction" .)