Rotate object to clicked location and walk there?

As per title, I am unable to get a unit to move to a clicked location on the map.

The below code is what I have done thus far. But only results in jittery movements from the unit with no odd rotation angles. I'm also hoping to clamp the y-axis so that the unit doesn't float away.

Any help will be greatly appreciated.

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class Movement : MonoBehaviour {
5.  
6.     public float rotationSpeed = 35.0f;
7.  
8.     private Quaternion _lookRotation;
9.     private Vector3 _direction;
10.  
11.     // Use this for initialization
12.     void Start () {
13.    
14.     }
15.    
16.     // Update is called once per frame
17.     void Update () {
18.  
19.         if (Input.GetMouseButtonDown(0))
20.         {
21.             RaycastHit hit;
22.             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
23.             if (Physics.Raycast(ray, out hit))
24.             {
25.                 if (hit.collider.tag == "Ground")
26.                 {
27.  
28.                     var worldPos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
29.                     _direction = (worldPos - transform.position).normalized;
30.  
31.                     _lookRotation = Quaternion.LookRotation(_direction);
32.  
33.                 }
34.  
35.                 transform.rotation = Quaternion.RotateTowards(transform.rotation, _lookRotation, rotationSpeed * Time.deltaTime);
36.  
37.             }
38.           }
39.  
40.  
41.     }
42. }
43.