If the pound cake is not under-baked but contains a moist, gummy streak somewhere in the cake (typically along the bottom or through the center of the loaf), the batter was most-likely over-worked. Over-working the batter by over-creaming the butter and sugar or beating too long or too hard after adding the flour will cause the cake to deflate after it’s baked, and the cake sinking down will lead to spots of compacted cake, which appears wet and gummy.