The speaker is lying in bed, speaking aloud to his own hand, which is an odd and oddly tender thing to do. The title, "Handheld," plays on the idea of something small you carry with you, but here the hand is both the thing held and the thing that holds. What he wants from it is clear enough: he hopes it might become "the fleet hand of a woman," quick and light, able to go out into the world and touch someone else.
The final lines turn that wish around. The hand is "ready to run / home to the chest," as if it would flee back to the body the moment it ventured out. That suggests a mix of longing and timidity. He imagines reaching toward intimacy, but the hand retreats to protect the heart. The mood is quiet, private and a little rueful, with loneliness showing through the humor of a man coaxing his own hand to be braver than he is.