Determination that might make roads safer? (4)
I believe the answer is:
grit
This clue is a double definition.
'determination' is the first definition.
(grit can mean determination or tenacity)
'might make roads safer?' is the second definition.
(added to icy roads)
'that' acts as a link.
(Other definitions for grit that I've seen before include "Small hard particles - determination" , "Courage (needed by chickens?)" , "Jock's enormous" , "Toughness" , "Small particles of sand etc" .)