create table t1(c1 clob);
insert into t1 values('abcdefghijklmnopqrstuvwxyz');
set serverout on
declare
c_lob clob;
v_txt varchar2(4000);
begin
select c1 into c_lob from t1;
v_txt := dbms_lob.substr(c_lob, 4000, 1);
dbms_output.put_line(v_txt);
end;
/
Will produce a line with the alphabet insert into t1 above.