I was working with Clojure a lot some years back, and I'm sure there's been a lot of progress in the ecosystem since then. However, what I learned then was that Clojure had an inherent startup overhead, because it had to get the language itself ready. The reason why you don't see this with for example Scala, which also runs on JVM, is because Clojure is very dynamic, as far as JVM languages go. Compare it to Java, for which the JVM was designed. These dynamic qualities come in part at the cost of the startup time.

I was especially frustrated by this, because I had spent some time writting a Clojure program that had to be able to cold-start fast. Decompiling the program's JAR and pruning out unnecessary classes gave a considerable speed-up, but it was not enough.