BCE0023: No appropriate version of 'UnityEngine.Transform.LookAt' for the argument list '(UnityEngine.RaycastHit)' was found.

I am trying to make a script for a rocket launcher with rockets that look towards where you point the mouse, so that if you hold the mouse over the target the rocket will aim towards it. I am using this code on the launcher:

var hit: RaycastHit;
if (Physics.Raycast(BarrelEnd.position, BarrelEnd.forward, hit)){

which works fine

and this code on the rocket

function track(tracker : RaycastHit){

which doesn’t work. I am a noob to unity and can’t find a way to fix this, so please could someone help.

You’re trying to look at a RaycastHit structure, what will never work. Look at tracker.transform or tracker.point instead:

function track(tracker: RaycastHit){
  transform.LookAt(tracker.transform); // it's transform, not Transform!

This makes the object look at the hit object position. If you pass tracker.point, the object will look at the hit point.