Add transparency to clipping plane shader

Hi guys, please help! How do I add transparency to this shader so that I can adjust its value through a script? I've looked at other examples and changed tags so that my objects have transparency; but I can't seem to adjust said transparency. Here is the shader I am using:

 Shader "Custom/ClippingPlane" 
 {
     Properties 
     {
       _MainTex ("Diffuse(RGB) Spec(A)", 2D) = "white" {}
       _section ("Section plane (x angle, y angle, z angle, w displacement)", vector) = (0,0,0,0.15)
       _Color ("Section Color", Color) = (1,1,1,0)
     }
     SubShader 
     {
       Tags { "Queue" = "Transparent" "RenderType" = "Transparent" }
       Cull Off
 
       CGPROGRAM
       #pragma surface surf Lambert alpha
 
       struct Input 
       {
           float2 uv_MainTex;
           float3 worldPos;
           float3 viewDir;
           float3 worldNormal;
       };
       sampler2D _MainTex;
       sampler2D _BumpMap;
       float4 _section;
       fixed4 _Color;
 
       void surf (Input IN, inout SurfaceOutput o) 
       {
         float toClip = _section.x * 0.1 * IN.worldPos.x +
                        _section.y * 0.1 * IN.worldPos.y +
                        _section.z * 0.1 * IN.worldPos.z + 
                        _section.w;
         clip( toClip);
         float fd = dot( IN.viewDir, IN.worldNormal);
         if (fd.x > 0)
         {
             o.Albedo = tex2D (_MainTex, IN.uv_MainTex).rgb;
             o.Alpha = tex2D (_MainTex, IN.uv_MainTex).a;
             return;
         }
         o.Emission = _Color;
       }
       ENDCG
     }
     Fallback "Diffuse"
 }

And here is the script I am using to change the alpha values:

 #pragma strict
 
 function Start () {
 
 }
 
 function Update () 
 {
     if (Input.GetKeyDown(KeyCode.Z) || Input.GetKey(KeyCode.Z))
     {
         Debug.Log("Key Z pressed");
         renderer.material.color.a -= 0.1; 
     }
     
     if (Input.GetKeyDown(KeyCode.X) || Input.GetKey(KeyCode.X))
     {
         Debug.Log("Key X pressed");
         renderer.material.color.a += 0.1; 
     }
     Debug.Log(renderer.material.color.a);
 }