Sounds like the lock screen play controls. This pops up if the iPad things you’ve got some audio playing that you may want to control without having to unlock the iPad.
Normally it’s the Music app, but from your description it is likely some other audio app. Perhaps a pocast, audio book, or radio station app. Normally the control panel goes away if the audio from the app is stopped when the iPad is unlocked.
In the case of the Music app all you have to do is open the app and make sure the music is not playing. Toggle it to be sure.
If the controls are not working, it’s likely that the app itself is frozen/unresponsive. Find the resonsible app, force close it, and the audio controls should go away.
Below are the controls for the Music app and Overcast (a podcast app). As you can see, they are slightly different. They both say iPad next to the icon because they are controling the iPad speakers. They would say Headphones or Bluetooth, or something else if the audio was being directed to those devices.
