I do agree with those above, I would most definitely not glue, or attach the clam itself to anything.
A couple tricks that I have learned-
When you first get a clam, if it is not already attached to a rock place it in the sandbed with a rock fragment barried underneath it. Give the clam a month or more to both attach itself to the rock fragment, and to get itself adjusted to the tank, and then move it to its final location.
With your tank however, I would be worried about the fluorescent lights getting it the light it needs. You can use your super glue to glue a couple rock fragments together, making a sort of pedistal. Glue the rocks so that they form a kind of dish around the clam, so that it doesnt fall off. It can then be placed right up next to the light. Give it a while to attach and then if desired, you could snap off the "sides" of the dish.