You can generate Maven’s POM out of Leiningen’s project definition and then use Maven’s dependency:tree plugin with a verbose option, like this:
$ lein pom
$ mvn dependency:tree -Dverbose=true
This will list dependencies omitted for various reasons, e.g.:
| +- ring:ring-core:jar:1.4.0:compile
| | +- (org.clojure:clojure:jar:1.5.1:compile - omitted for conflict with 1.7.0)
| | +- (org.clojure:tools.reader:jar:0.9.1:compile - omitted for conflict with 0.10.0-alpha3)
| | +- (ring:ring-codec:jar:1.0.0:compile - omitted for duplicate)
For more options to dependency:tree see its documentation.