No se puede ejecutar la consulta sql

Solo es posible con sql dinámico, ya que el número de columnas en la cláusula group by es variable. Por ejemplo, con una función:

    create or replace
    function sum_cash_transactions ( p_threshold_type varchar2) return number
    is
      v_result NUMBER;
    begin
      execute immediate ' select max( sum_amount) 
                          from( select sum(amount) as sum_amount
                                from   cash_transactions
                                group by ' || p_threshold_type || ' )'
     into v_result;
     return v_result;
     end;
/

y luego

select threshold_id
 from thresholds
 where threshold_amount < sum_cash_transactions(threshold_type);

EDITAR debido a nuevos requisitos:

CREATE OR REPLACE package pkg AS
  TYPE res_rec_type IS RECORD (
    threshold_id  VARCHAR2(200)
  , Tran_inst_id  NUMBER(10,0)
  , sum_amount    NUMBER(22)
  );
  TYPE res_tab_type IS TABLE of res_rec_type;
  FUNCTION f1 RETURN  res_tab_type PIPELINED;
END;
/

CREATE OR REPLACE PACKAGE BODY pkg AS

  FUNCTION f1 RETURN  res_tab_type PIPELINED
  IS
    CUR    SYS_REFCURSOR;
    v_rec  res_rec_type;
  BEGIN
    FOR treshold in ( SELECT Threshold_id,  Threshold_type,   Threshold_amount FROM thresholds)
    LOOP
      OPEN CUR FOR 'SELECT ' || threshold.Threshold_id || ', tTran_inst_id,  s FROM (SELECT  tTran_inst_id, SUM(AMOUNT) OVER (PARTITION BY ' || p_Threshold_type || ') as s from cash_transactions ) WHERE s > ' || treshold.Threshold_amount ;
      LOOP
        FETCH cur INTO v_rec;
        EXIT WHEN cur%NOTFOUND;
        pipe row(v_rec);
      END LOOP;
    END LOOP;
    CLOSE cur;
    RETURN;
  END;
END;
/

SELECT * form table(pkg.f1);