This JAR is available since Clover 4.0.6.
In order to run an application instrumented by Clover, you must add clover.jar (the com.atlassian.clover:clover artifact) to the runtime classpath, otherwise your application will fail with the NoClassDefFoundError.
You can also use the clover-runtime.jar (the com.atlassian.clover:clover-runtime artifact) for this purpose. This JAR contains Clover's runtime classes only (e.g. it cannot be used for compilation or reporting) and thanks to its reduced size, you may bundle this JAR into your application's JAR. Thanks to this, the deployment process may be a little bit simplified as there would be no need to copy clover.jar and to add it to application's classpath.