This document explains how to clear Safari's saved passwords and form data on iOS.Note: These screenshots were taken from various iOS devices, the general procedure should apply.
Locate and tap the Settings App.
Scroll down and tap the Accounts & Passwords option.
Tap App & Website Passwords. You may be asked to enter a passcode, or authenticate with TouchID or FaceID.
You may delete between one or all passwords.
Swipe left on the item you wish to delete, and press the red Delete area when it appears.
Tap Edit in the top right corner, then select all of the items you would like to remove, then tap Delete.