If your iTunes application on Mac have updated to Version 11+, you can use the method Apple supported to show all duplicate items in your iTunes library. From the menu at the top of your computer screen, choose View > Show Duplicate Items. And then manually delete unwanted ones. Or if you are a Windows user, Hold down the Control and B keys on your keyboard to open the iTunes menu bar. Choose View > Show Duplicate Items.
Matches are based on the song name and artist. If you have multiple versions of the same song (for example, live and studio versions, or versions from different albums), hold the Alt or Option key (Mac) or the Shift key (Windows) and choose View > Show Exact Duplicate Items. This will show only the duplicate songs that have the same name, artist, and album. The information in the other columns, such as Time, Release Date, or Genre, can also help you determine which item to keep and which to remove. For example, the Plays column shows which version of the song you've listened to more.
For more details, check: Remove Duplicate Songs from iTunes