See the https://answers.atlassian.com/questions/29425/clover-error-when-installing-in-grails-project

Problems:

#1) Clover does not install properly if it's being installed via dependency defined in BuildConfig.groovy, instead of command line "grails install-plugin". It cannot find Clover ant task definitions just after installation.

#2) Clover does not instrument groovy sources in Grails 2.x - the reason is that Clover "hooks" to the GrailsCompiler class which has been removed in Grails 2.x, instead of this we have Grailsc now.

#3) A problem with "static class FileOptimizable" - already fixed in CLOV-1076/CLOV-1093

#4) Dependencies in BuildConfig.groovy

build(clover.core.version, changing:false)
compile(clover.core.version, changing:false)
runtime(clover.core.version, changing:false)

are causing installation warnings in Grails 2.x because of "changing:false" property.