Wander out of terror (3)
'wander' is the definition.
'out of terror' is the wordplay.
'out of' indicates the answer is hidden within the clue.
'ERR' can be found hidden inside 'terror'.
(Other definitions for err that I've seen before include "Go astray", "Bungle", "Stray from the straight and narrow", "have an affair?", "Slip up".)