I may be wrong, but this seems to have changed for me in the last day, quite possibly because I’ve selected something unwittingly.
Currently, when I click on a word, the sidebar automatically opens, squeezing out the text. I’m sure that it didn’t do that before, but just showed a pop-up definition, and if I wanted to see more I needed to click on the sidebar symbol.
Update
It’s now gone back to normal on all my devices.