As @closetnoc said above, your deep link pages may outrank your home page for a long tail keyword. This is possibly because that page is optimized for that phrase or keyword, while your home page may be optimized for other search terms.
If you want your home page to rank for "ethical design agency" you have to optimize your home page, to the point where it'll be more optimized for it than the deep link page. (Whether that makes sense for your business is up to you to decide: would you lose rankings for other keywords that figure on your home page?) That means including the phrase in your title tag, structured data description field, heading and body copy, image alt text - the usual SEO keyword optimization techniques.
The other course you can take is make your deep link page, which is already ranking for the term, more relevant to the term and to your business goals. That means adding content, further optimization, CTA's, etc.
Also, your ethical design page may rank above your home page if it has more backlinks that are relevant to that term. Use a tool like Moz's Open Site Explorer to compare the backlink profile of both the home page and ethical design page. If the latter has more links from external websites - or one link from a really authoritative one - that may be your answer. Your options at that point would include contacting the webmaster(s) and asking them to link to the home page instead of the deep content page.