Using rest stroke (apoyando) this can be made very clear. As always, the way to approach a piece you find difficult is to start off slow.
- Find a speed at which you can comfortably play this
- Ensure you play it accurately
- Choose which fingers you are going to use (to me this feels like apoyando with i, m and a, but you may wish to play it differently)
Then gradually increase your speed. If you find you are tense or tiring, make a conscious effort to relax. You should also try altering the angle of your right hand, as some positions will be faster than others. Generally work towards finger movements at 90 degrees to the strings.
Apoyando should pluck the string then come to rest against the next string. To ensure clarity of sound, it is straightforward to only allow the chosen string to sound, with all others damped as needed.