Are you living in the country that issued it?
YES —When you get back home, ask the authorities there for a duplicate.
NO —I live in another EU country
If you lose your driving licence or have it stolen while travelling abroad, you should contact the local police and your consulate or embassy to find out what to do.
They may issue a provisional document that allows you to drive in that country for a short time.
When you get back home to the country where you live, you'll have to get a new licence from the authorities there. It will be a new licence issued by that country, rather than a duplicate of your old licence.