Accidentally deleted the Clock app

You can’t delete the clock app, so most likely it got moved to another page of the Home screen or into a folder. Use Spotlight search to verify that it is still on your phone; it it is in a folder the search will show the name of the folder. Otherwise just check carefully on all of your Home screen pages.

See—>Use Search on your iPhone, iPad, or iPod touch - Apple Support

You need to go ( swipe ) all the way to the rightmost page. There you should find the clock. Next you‘re going to hold down-press ( force touch or whatever apple calls that ) on the clock and select "add to home screen".

If you can‘t find the app there then try and look for it in the app store.

Hope I could help :)