What the flip is a succubus

Succubus is understood as a Lilin-demon in female form or supernatural entity that appears in dreams to seduce men, usually through sexual activity. [1] The descriptions of the same can be traced back to the folklore of medieval times.

a female demon believed to have sexual intercourse with sleeping men.

Explanation:

your word would be isle.

isle is an island or peninsula especially a small one.

if you add the letter "a" you get aisle, which is a passage between 2 rows of something like chairs, shelves, or something else.