In this way, one’s sure to have an impact (9,6)
I believe the answer is:
Here is my best explanation:
'in this way' is the definition.
The definition suggests a singular noun which matches the answer.
'one's sure to have an impact' is the subsidiary indication.
I cannot quite understand how this works, but
'one's' could be 'is' (resembles I's) and 'is' is present in the answer.
an anagram of 'sure' is 'urse' which is present in the answer.
'an' could be 'i' (Roman numeral for one) and 'i' is present in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for collision course that I've seen before include "Dangerous approach", "what looks like leading to conflict", "leads to certain conflict" and "opposing philosophies leading to conflict".)