SQL & PL/SQL :: Read CLOB And Use In SQL Query?

I have a small doubt on CLOB reading and not able to do it in the query because it has very large strings in it.

create table TEST
(
col1 VARCHAR2(100),
col2 VARCHAR2(100),
col3 VARCHAR2(100),
col4 DATE,
col5 CLOB,
col6 BLOB,

[code]....

This data I am inserting from front end into test table via XML but here i just giving insert statement.Now , I have below query to insert the data into different table:

This query is working for col3 ='2' as its small string but for col3 ='1' its not working and giving character string buffer too small.

with indata as

(select 1 sn, (select dbms_lob.substr(col5) from test where col3 = '1') x
from dual
union all
select 2, null x from dual),
t1 as

[code]....