SQL & PL/SQL :: Function Returning CLOB - Invalid Format

I have a problem when trying to create a PLSQL function based on an XML extraction query.

I have three dummy tables:

SQL> get create_address
1 create table ADDRESS
2 (
3 id NUMBER not null,
4 house_number NUMBER,
5 house_name VARCHAR2(20),
6 street_name VARCHAR2(30),

[code]....

And the following dummy data for these:

1 insert all
2 into ADDRESS (ID, HOUSE_NUMBER, HOUSE_NAME, STREET_NAME, CITY, COUNTY, POSTAREA, POSTSTREET)
3 values (1, 1, '', 'Tube Street', 'Norwich', 'Norfolk', 'NF12', '2DF')
4 into ADDRESS (ID, HOUSE_NUMBER, HOUSE_NAME, STREET_NAME, CITY, COUNTY, POSTAREA, POSTSTREET)
5 values (2, 5, '', 'Dave Street', 'Edlington', 'Kent', 'CT34', '8GH')
6 into ADDRESS (ID, HOUSE_NUMBER, HOUSE_NAME, STREET_NAME, CITY, COUNTY, POSTAREA, POSTSTREET)

[code]....

So far so good then. But, what I want to create is a function where I can pass in an id value and return the corresponding XML CLOB.

So I try, very simply, this:

SQL> get get_xml_data
1 create or replace function get_xml_data(p_id in number) return clob is
2 Result clob;
3 begin
4 select xmlroot(xmlelement("HomeData",

[code]....

And, alas, i'm greeted by this:

SQL> /
Warning: Function created with compilation errors.
SQL> sho err
Errors for FUNCTION GET_XML_DATA:
LINE/COL ERROR
-------- -----------------------------------------------------------------
4/5 PL/SQL: SQL Statement ignored
24/63 PL/SQL: ORA-00932: inconsistent datatypes: expected NUMBER got -
SQL>

I've tried to redo the query in several different ways but so far nothing.