Ice creams dropped on the motorway (5)
I believe the answer is:
cones
I believe this clue is a double definition.
'ice creams' is the first definition.
(ice cream cones)
'dropped on the motorway' is the second definition.
(cones may be placed on a road)
(Other definitions for cones that I've seen before include "Round shapes with tapering sides" , "subject of a former hotline" , "Ice-cream holders or fruits of pine trees" , "Shapes of wafers for ice-cream" , "Cornets" .)