There are many WordPress themes that can be suitable for an expert platform like Clarity, depending on your specific needs and preferences. Here are a few popular options:

Expertly: This theme is specifically designed for expert platforms and features a customizable homepage, expert profiles, and integration with popular plugins such as WooCommerce and BuddyPress.

Divi: Divi is a versatile theme that can be customized to create a range of websites, including expert platforms. It features a drag-and-drop builder and a variety of pre-built templates.

Consulting: Consulting is a professional theme that is designed for consultants, coaches, and other experts. It features customizable pages and templates, as well as integration with popular plugins such as Contact Form 7 and Yoast SEO.

As for examples of successful expert platforms, in addition to Clarity, some other examples include:

UpCounsel: UpCounsel is a platform that connects businesses with freelance lawyers. It offers a range of legal services, including contracts, employment law, and intellectual property.

Toptal: Toptal is a platform that connects businesses with top freelance developers, designers, and finance experts. It features a rigorous screening process to ensure that only the top 3% of applicants are accepted.

Thumbtack: Thumbtack is a platform that connects consumers with local service providers, including home repair, personal trainers, and event planners.

These platforms have been successful in part because they offer a valuable service that meets a specific need, and they provide a user-friendly platform for connecting experts with clients.