Sitting here in front of a screen on the other end of the planet, those look like perfectly normal and harmless casting "flow" marks, which you'll find in many cast aluminum parts throughout every motorcycle.
In fact, this is a common question on forums for modern bikes whenever an owner gets a peep at the unfinished surface of a cast aluminum part. (Clutch baskets and wheel hubs, most often.)
However, as mentioned above, you're the one with the part in hand. If the surfaces of the clutch basket show signs of abuse, or you know the it came from a bike with a history of drag racing, or just for your own peace of mind, you can have it inspected using dye. Or even buy a dye inspection kit and check it yourself -- they're not that expensive.
In fact, this is a common question on forums for modern bikes whenever an owner gets a peep at the unfinished surface of a cast aluminum part. (Clutch baskets and wheel hubs, most often.)
However, as mentioned above, you're the one with the part in hand. If the surfaces of the clutch basket show signs of abuse, or you know the it came from a bike with a history of drag racing, or just for your own peace of mind, you can have it inspected using dye. Or even buy a dye inspection kit and check it yourself -- they're not that expensive.