@Steve181257: Please can you confirm the model name and current Android version of the device you're experiencing this issue with? The information can be found in Settings > About Phone > Model name (towards the top of the screen) > Software information > Android version.
Please can you also clarify which clock icon you're referring to?
If you press and hold on an empty area of your Home Screen > Widgets > Clock > Swipe to your preferred option > Add, you can resize the chosen widget by dragging corners of the surrounding blue box.
@Steve181257: Are you referring to the Clock app? You mentioned that you could still access it by heading to Settings > Apps > Open, so it should still be installed on your Galaxy A12. With this in mind, please swipe up from your Home Screen, and use the search bar at the top of the screen to manually search for the Clock app. Press and hold on the resulting icon, and tap on 'Locate app' to take you to its current location.