This is a charade - two separate parts are joined together to form the answer word.
Look for a word meaning 'barrier' (3 letters) and combine it with a word meaning 'to become weaker, perhaps' (3 letters). The word 'to' signals the joining of these parts.
Answer: DAMAGE | DAM (barrier) + AGE (to become weaker, perhaps) = DAMAGE (a likely result of crash)