Hey Leanne,
this is not a single post, rather a category page. All archive templates in Ikebana, including category pages, have sidebars. In order to remove the sidebar from this particular page, you’ll need the following CSS code:
.category-photography #content { width: 100% !important; }
.category-photography #sidebar { display: none; }
Sincerely,
Andrii / Satori Studio