It is Chopin's Waltz in E minor. It is thought to have been written when he was around the age of 20, but it was not published during his lifetime so it has no Opus number.
in some Waltz collections it is given as number 15, in others as number 16
It is usually played a bit quicker and with more brilliance and snap than the snippet that you have found

<-- "clever" or "less tired" ???????