There are many companies using Clojure large and small, nobody actually using the language has problems hiring people for it. This is not a theoretical debate, there's no evidence to support the notion that Clojure is hard to hire for.

In practice, the language is a small part of what a new hire has to learn. Each company has different processes, tools, workflows, frameworks, and so on. A language is only a small part of that.

While there are obviously companies where Clojure wouldn't be a good fit, the reasons wouldn't be that it's hard to train new people to work with it.