TinkerPop 3.x is in wide use across many open source and commerical graph databases. Ogre compatibility with 3.x makes it straightforward for any Clojure project to work with those systems.
Java interop with Clojure, especially with the Gremlin traversal language is clunky. Ogre smooths those rough edges for a better way to work with Apache TinkerPop-enabled graphs.
Apache TinkerPop has an extensive public API, but Ogre focuses on wrapping the Gremlin traversal language, which is the primary way users interact with TinkerPop-enabled Graphs.