I have configured a connector (RSS) in Find and the data is correctly indexed.
Now if I delete the connector, i want to delete all the associated content in find index.
What is the best possible way to delete all the content related to a particular connector in FIND (besides clearing the whole index )?
Have a look at this documentation page about deleting documents from Find.
Basically you can delete documents from the index by content type and/or certain criteria. So if you can deduce some characteristics about your old RSS data, then this may work for you.
When you delete a connector it should cleanup all content it has crawled and provided to the index.
If it doesn't please reach out to us in support and we can help you.