It's hard to say if the clown is just storing it's food in a nice safe anemone or if the clown actually attempts to feed the anemone, both are harmless though. They do make for very enjoyable viewing though!
I had a male maroon clownfish that would feed a Sherman BTA. You could tell when he was feeding. When I fed the tank and he swam straight to the food and then turned back to his nem and swam straight back he always ate the food. But when he swam out to get the food and then swam backwards to the anemone he always dropped the food on the nem. It was always after he had eaten though so I think it's more of a store it for later rather than making sure his ol buddy the anemone got some food.