By default, the clear button, when clicked, clears the associated controls on the Advanced Search Form. For Non Associated controls, you need to write code manually for clearing the controls. Sometimes, for the same clear button click event, you may need to clear the data grid.
To do that, execute the query in such a way that only the structure of the resultset is obtained, without data. (Ex: "select * from PartyMaster where PartyID=-1")