all you need to do is anchor the elephant down well -- for example build a nice long skewer in each of his back legs that can be inserted into the board underneath the cake -- stick it in there and the umbrella ain't going no where -- i'd put it in at an angle so that the tips of the skewer actually go/point under the body of the elephant --
best to you
Not sure if this is answering your question but this is what I'd do:
Use fondant mixed with cmc to stiffen it.
Roll out a round piece of yellow fondant, cut out the edges half round with f.e. a tiny measuring cup upside down. Place it in a cup to dry into shape (sort of half ball). Make the umbrella stick out of fondant and insert a taped wire which sticks out on one end and a small yellow fondant plate in a 90' angle at the other end. Dry. Glue umbrella onto the stick, using edible glue between the umbrella and the yellow circle (the yellow circle gives it a bit more surface to attach). At the same time make the Elefant. Dry too. Then insert wire which is sticking out from the umbrella stick into elefant's trunk using edible glue.