You have to create the index for the full table(All the seven partitions).if you are sure that you will not use any dml opertions in the other 6 partitions .You have to redo the design of your application slightly.

1.create a table structure similar to the partition table.
2.do the exchange partition with the newly created table.
3.do all your dml operations on the new table.

Modify your applications for the same.