Rotate object: script works if applied to that object, but not if referencing object in scene

Hello,

I want to rotate the hands of a clock every time the clock is clicked on.

However: although the script below works fine to translate the entire clock. When I replace this line:

 transform.rotation= Quaternion.Lerp (transform.rotation, targetRotation , 10 * smooth * Time.deltaTime); 

with this:

 minuteHand.transform.rotation= Quaternion.Lerp (transform.rotation, targetRotation , 10 * smooth * Time.deltaTime); 

The rotation no longer work properly, but starts jerking between 4 and 7 degrees and doesn't stop moving. Does anyone know how I should write the script so I can rotate a gameobject in the scene, rather than the object the script is applied to?

 public class ClockScript : MonoBehaviour {
 
     public GameObject minuteHand;
     public GameObject hourHand;
 
     public float clockAngle;
 
     public float smooth = 1f;
     private Quaternion targetRotation;
     void Start(){
         targetRotation = transform.rotation;
     }
 
     void Update () {
         if (Input.GetMouseButtonDown(0)) { 
             targetRotation *=  Quaternion.AngleAxis(clockAngle, Vector3.forward);
         }
         transform.rotation= Quaternion.Lerp (transform.rotation, targetRotation , 10 * smooth * Time.deltaTime); 
     }
 }

All the best, Laurien