Radish of the Damned

> Move Plant

Tear the broken door wood into splinters (I would have made the condition not to use up all the wood this way, but there is another door as yet untouched from the room we originally came from so if you need to use all of the broken door wood use it all).

then

> Move Plant

Spread the splinters out so that they form a loose wall of splinters that takes up the entire breadth and height of the hallway, and then propel them forwards.

By doing this you may be able to find a spot where the invisible thing does not protect, or if it is some kind of shield overwhelm it by forcing it to try to protect a large surface area at once.