。
Make it clear whether you can come or not.
Literal
Come-can [nominalizer-の] whether-or-not clear do-give-me.
~のかどうか is the 'whether or not X' embedded question structure — のか (embedded question) + どうか ('whether or not'). はっきりする ('to become clear') is the verb form of the na-adjective はっきり ('clear'). ~てくれ is the casual imperative. 来られる is the ra-less potential of 来る.