Here's how it works:
* leisure: This is the base word, meaning "free time or inactivity."
* -ly: This is the suffix that turns a noun or adjective into an adverb, indicating manner or way.
So, "leisurely" literally means "in a manner of leisure" or "slowly and relaxed."
Therefore, while "-ly" is a part of the word, it's not a suffix of "leisurely" itself.