Declare
  Itm1 varchar2(30) := :system.trigger_item;
Begin
  CLEAR_FORM(NO_VALIDATE,FULL_ROLLBACK);
  :B1.NEW_FORM := :SYSTEM.CURRENT_FORM; --Here B1 is the Block Name
  Go_Item(Itm1);
End;

Declare
  -- LF: store item for which the trigger is firing into Itm1 variable
  Itm1 varchar2(30) := :system.trigger_item;
Begin
  -- LF: clear form, i.e. remove all records from the form. By default, input focus
  --     is the first item of the first block
  CLEAR_FORM(NO_VALIDATE,FULL_ROLLBACK);

  -- LF: store name of the current form into a block item
  :B1.NEW_FORM := :SYSTEM.CURRENT_FORM; --Here B1 is the Block Name

  -- LF: You don't want to set focus to the first item of the first block (as CLEAR_FORM does), 
  --     but the item you saved into Itm1 variable within the DECLARE section
  Go_Item(Itm1);
End;