Clowns, like other damsels will take larger pieces of food and spit them into the rocks (for damsels) or an anemone (for clowns). The intention, if one can judge intent in a clown/damsel, is to save the food for later and/or eat it in peace (away from other food competitors). The result is that clowns put their food in the anemone, and the anemone consumes it (often while the clown is chasing down other food in the tank).
It appears to be an unintended consequence, as in many cases, when the clown is full, they often start pulling food out of the tentacles of their host and spitting it back into the water column (dang clowns are very exacting about what can be in their anemones! :lol: ) - in essence accomplishing the exact opposite of feeding the anemone (unfeeding?). Again, an apparent unintended consequence due to other natural behaviors being played out.
FWIW,
Kevin