It's gay incest. A clone is just a child with one parent after all, so it's incest, and they'd be the same sex as you so it's gay (or lesbian if you are a lady).
How old is the clone and have you interacted with each other before? That would make it worse/less worse, depending on if you have a family relationship already or if there's a big age gap and power imbalance. It'd be more forgivable if you found out you had a long lost clone the same age as you and you'd never met before and then you got together in some weird cope, than if you grew your own clone and groomed it from childhood to be your sweetheart from the ground-up.