playing Words. pop up ad wont delete

If you're talking about this app:--> https://apps.apple.com/us/app/words-with-friends-word-game/id804379658, I suggest that you contact their developer team and ask them. Use these instructions:--> How to contact an app developer - Apple Support

Regards

Giulio

Many “free” Apps are monetised through advertising. Many (but not all) Apps that feature advertising pop-ups have an in-App purchase - that if paid, will suppress unwanted adverts.