Is the goal to protect the Bela or to implement a nicer-sounding clipping when it does clip?
To simply protect the Bela, I think giuliomoro suggestion is the most simple. Use a series resistor before the diodes to limit the current into the diodes (something like 1k).
If you want a less harsh-sounding clipping when it does limit, then something more elaborate can be added to the filter.
Because my project is guitar-related, I'm considering doing a pre-emphasis filter at about 700-Hz (like a Tubescreamer) followed by the clipping stage. Then the final output will be scaled to +/-1.0V for the audio input. Then the de-emphasis filter will be applied in software (the CODEC actually has a configurable de-emphasis filter built-in). Boosting the highs (or cutting the lows) prior to clipping reduces the amount of intermodulation distortion and this generally sounds nicer than hard limiting.
The pre-emphasis also helps the audio quality for a typical musical instrument source. The higher frequency components of a musical instrument are typically lower amplitude than the fundamentals, so by emphasizing these you get a better effective resolution overall. This type of concept has been used for improving dynamic range on limited media (like magnetic tapes) for a long time. It is still valid for digital systems because the nature of musical instruments hasn't changed.
The pre-emphasis frequency should be selected according to your intended instrument/input source.
Just some musings you may find helpful.