AB,
if I understand correctly you see the 10mV noise on the output of the clock generator correct? How are you measuring this noise? I want to make sure it is not just picked up by the scope probe rather than actually being in the signal. Do you see that noise on the high level only of the clock or also on the low level?
Can you post a picture of the scope measurement and maybe even a picture of your set-up while measuring?
Is it a differential clock signal or single ended?
We need to differentiate between conducted noise versus radiated noise. Conducted noise is handled through filtering between the power supply and the clock circuit.
Radiated noise (actual EMI) would need to be addressed through layout or shielding. If your layout is not optimal then it's possible that there is some coupling between the circuits. But 10mV on a clock signal seem high for radiated coupling.
The snubber would not improve conducted noise much and may only improve radiated noise if the layout is already well done.
LucaV