How to calculate the average on a time window (ignoring date)

Is there a way to calculate the average in a certain time window ignoring the date? I have a need to get the average on certain time intervals…

Example:

00.00h - 00.10h - <field average>
00.10h - 00.20h - <field average>

So i would like to get an average on certain timeslots without the date values. The normal mean() method takes into account the actual dates.

Any hints or tips on if and how this can be done using InfluxDB sql?