It is a good idea. Instead of a clam, this seemed to me like more of a snail thing to do. Snails are clam cousins so it is close. Plus snails already live on land, and your tree canopy seems like snail heaven. I went looking.
This quote is about the "pond snail" of which the Lymnaea species is one.
The snail leaves an underwater slime trail, which collects plant and
animal debris as well as microscopic organisms. Upon crossing its own
slime path, the pond snail eats the bits and pieces stuck to the trail
Better is this great stuff on pond snail feeding I found on Google books from Behavior monographs.
Cambridge, Mass. : H. Holt & Co., 1911. I love these old natural history descriptions!
All of these flesh eating snails have been seen eating dead
houseflies, mayflies, fish, beefsteak and snails. They will eat such
meat fresh, although they seemingly prefer it stale. I had seen them
eating dead snails, when the odor from the food could scarcely be
endured in the laboratory. The Lymnaea cited above have cannibal
traits, a character which is especially notable in L. stagnalis. I
have seen this species devouring struggling flies, moths and young
snails that have become entangled in its slime…
It is a common thing to see Lymnaea stagnalis and other freshwater
pulmonates turn about and eat from the foot the mass of somewhat
hardened mucus together with what foreign bodies this has
incorporated. Linden (1902) has observed the dexterity of Lymnaea in
obtaining food from the foot, while the snail is moving upon the
surface film. Brockmeier (1898) describes this process as “plankton
fishing”. The mucus servers not only as a food itself but is a most
efficient means of collecting food for the snail, both on solids and
on the film. The trails of mucus left on solids remain sticky and
serve as a trap to catch my new plants and animals and other foreign
particles. The snails eat continually from the solids, devouring the
mucus with all that is caught in it.
So: a mollusk which secretes sticky mucus from the foot, then eats the mucus with live prey that has stuck to it. That is what you want and that exists! A snail would probably not mind being sessile most of the time, waiting for its prey to come to it.
It is one more step to having attractive smelling mucus. I could imagine mucus that stunk could attract flies although that might attract larger carrion feeders too which would eat the snail. The same problem exists for fruit smells - fruit flies are tasty but big things like fruit. Mucus that smelled like flowers could attract pollinators - that sounds right.
I was thinking of this concept and a snail that let its viscous slime net drool down thru the air like flypaper. Then it would reel it back in with its haul of bugs.