Technically true, but I don't think it makes sense to consider Clojure to be the same thing as Lisp in the context of ternaryoperator's statement (though I obviously can't speak for him). Notably, Clojure's tight integration with Java is the primary reason for its relative popularity, and what most sets it apart from the rest of the Lisp family. It is disingenuous to claim Clojure means Lisp has gone mainstream when the popularity of Clojure is not due to its inclusion in the Lisp family.
Beyond that, I'm not quite sure Clojure counts as "mainstream" yet. According to the TIOBE Index, it doesn't even rank in the top 50 languages. Heck, the top 20 includes R, and Dart, neither of which I would call "mainstream" (I'm actually really surprised at how high R is ranking). I don't know how significant that is, though the TIOBE Index is measuring "number of skilled engineers world-wide, courses, and third party vendors" and that seems like a reasonable approximation for "mainstream" to me.
There are several languages targeting the JVM these days. And, what obviously sets Clojure apart from other JVM languages is its Lispiness (i.e., the JVM is constant across JVM languages).
Clojure is not married to the JVM either-- in fact, it has been hinted that it would jump ship if something better comes along or the current situation becomes less viable. Furthermore we already have a dialect of Clojure called ClojureScript which targets JavaScript/node/V8.
And, I look at the JVM as really merely a library/API/runtime. C++ has STL and stdio and such and they are not part of the language proper but rather merely libraries for interacting with the underlying operating system (in a platform independent way). The same is true for the JVM with respect to Clojure and Scala et al.
Perfect example. Clojure != Lisp. But it is a pretty obvious descendant.