A skeleton key has been “reduced to its essential parts.” 
Revising a poem to what you want to say—need to say—is much of the work required on your journey to create something worthwhile. As you craft a poem, you sculpt language, razor away distraction, dissolve false paths, abolish esoteric digressions, and so on—until you have done the hard labor that encourages a valuable reading experience with a generous, thought-provoking takeaway. Each poem is the wheel anew, conjured as if out of nothing.
Managing Editor for the SVJ
 Collins English Dictionary