I want to make ajax call to module functuion
Please reread the documentation to drupal ajax documentation, particularly how Drupal behaviours do work.

You are missing one crucial part. Drupal calls the attach-function of your behaviour on documentReady or before DOM-elements get injected into the current document. As your JS-code does not have an attach-method, nothing happens. The code below should give you an idea how to fix your problem:

Drupal.behaviors.custom = function (context, settings) 
{
  attach: function(context, settings) {
    $(document).on('click', '#clear-filter', function() { 
      console.log("Hello");
      jQuery.ajax({
        type: 'POST',
        url: 'custom/field-work',
        dataType: 'json',
        success: function(data){
          console.log(data);
        },
      });
    });
  }
};