Combining CLOB columns in Query

Question

I have a table with a CLOB column. What I need to do is query the table, and combine the CLOB column of each row into a single CLOB column.

So, say I have something like:

ABC      CLOB_VALUE1
ABC      CLOB_VALUE2
ABC      CLOB_VALUE2

What I need at output is:

ABC      Combined Value (CLOB_VALUE1, CLOB_VALUE2, CLOB_VALUE3)

LISTAGG will not work due to the length, and I'm not having any luck with XMLAGG (unless I am doing it wrong).

I tried this, but it is not retrieving all the records:

SELECT id, XMLAGG(XMLELEMENT(E,price_string||',') ORDER BY 
        price_date).EXTRACT('//text()').getclobval() AS daily_7d_prices
FROM daily_price_coll
WHERE price_date >= TRUNC(SYSDATE) - 7
GROUP BY id;

I'm only getting the most recent row, when there are actually 3 rows in the table.

Any ideas?