Whenever a player hits a top there are three things that may have happened. One might simply be distance away from the ball or ball position left or right in the players stance. Use alignment sticks and make sure you’re not too far away from the ball address or that you have the ball either too far forward or too far back in your stance.
The next thing to check is your club path you can top a ball by either being too far outside in or too far inside out. Easiest way to check and see which one is your issue is to use the cardboard box your set of irons came in and place it outside your target line with the toe of your club touching the box at address.
If you are outside and you will hit the box before you hit the ball. And if you are inside out you will hit the box after you hit the ball. Either way the box drill should get you back on track in no time.