Slips
'slips' is the definition.
('err' can be a synonym of 'slip')
This is all the clue.
(Other definitions for errs that I've seen before include "Makes a mistake" , "Strays" , "Goes astray" , "Boobs" , "Is mistaken" .)
'slips' is the definition.
('skid' can be a synonym of 'slip')
This is all the clue.
(Other definitions for skids that I've seen before include "Slides sideways" , "From coasts" , "Slides without control" .)