When I add a context filter, my view is wrapped in a div
Check the twig template (by turning on twig debugging) that is generating the div for your contextual filter. Then alter it with an ID or Class tag. 

Let me know if you need help turning on twig debugging.  

Find the twig template that is generating that div, copy it and rename it with one of the FILE NAME SUGGESTIONS. The add the following code to the div. 

&lt;div{{ attributes.addClass('my-class') }}&gt;&lt;/div&gt;