A woman with cleats is walking on someone's back, but she doesn't want to hurt him. She has to be very gentle. Cleats are sharp and pointy, and not designed for back walking, so she's being extra, special gentle right now.
Actually, the person she's being gentle with is her dad (だ). No one would ever want to hurt their dad, especially if he's asked you to walk gently on his back as a way of giving him a massage.