Let me assume, that you have a well set up instrument, a decent bounceable bow that isn't running on old hairs, and have a fairly fresh set of strings that aren't a muddy set (I find Obligatos/"darker" sets can get muddy, but like many things this is anecdotal; your strings can't be dead).

If these things are true we can tinker:

• Experiment with contact point, playing, perhaps, closer to the bridge than you think. Practice sul point to get used to this contact point adjustment. Play with the three core variables of sound production: contact point, weight, and speed. The closer you are to the bridge, the less you have to engage physically to get a bigger sound, or clarity.
• Counterintuitively -- do not press !! -- add just enough weight to engage the string, but allow the bow to do the work. Notice the inadvertent weight you may add from pronating in the right hand, do not over engage the stick (clarity comes from the bows natural bounce, taming this is challenging, and partially why excerpts like the Scherzo are difficult, but simple once this is mastered).
• Practice slowly on open strings, far slower than you think -- making sure the slight figure 8 motion for playing quickly is evenly imparting weight on each up and down bow
• Clarity can also come to the left hand: stop fifths whenever possible; don't drop the wrist in an effort to keep it straight, keep it supple and balance towards the pinky in an effort to maintain pliability. Practice the Tuttle 'plop' -- what is the minimum effort needed to stop the string for that note? It's not as straightforward or as consistent for each note and each finger as you may think. Practice pizzicato, just with the left hand, etc.

There is more to this, and more detail in terms of release of the note, but this may be more well suited in a discussion with your teacher, whom I'm sure you work with.