Hi,
I have small circle below bigger one and I want to crop shadow, which is dropped by bigger one only to small circle, not to white background. I tried many operations, but I'm still not able to cut that small part of shadow


What are right steps to do it, please?

Use a clip:
http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Clip.html

which has the shape of the larger circle unioned with the smaller one:

select both (Shift+Click),
duplicate (Ctrl+D), Ctrl++,
then select this new path and the big circle with the shadow
and apply this clip to it - must be on top, then do Object -> Clip -> Set

Doesn't it depend on how the drop shadow it created? The steps Moini gave will work if the drop shadow is made with the Drop Shadow filter.

But if the drop shadow is made with a duplicate of the large circle, the steps are slightly different. In that case, these are the steps:

select both (Shift+Click),
duplicate (Ctrl+D), and Union (Ctrl++),
then select this new path and the shadow object
and apply this clip to it - must be on top, then do Object -> Clip -> Set

Thank you guys

Now that's a weird circle...