Give them a preview
That way, shoppers can quickly get the essence of what the product is about, and read more if they want to.
I like how IKEA has done it, with a Read More link that scrolls the page down to the extended Product Description section.
Lower on the product page is the detailed description:
Add a Read More link
From memory, I haven’t seen that Read More link very often at all. For example, Amazon doesn’t have it. I think it would be something good for you to test.