- OK, this is the first of the four attachments to be free from. tse 'di as mentioned before is this life, la is pointing to this life from something on the right side, or zhen. zhen is attachment, na is a particle defining when, and what it points to on the right side is chos pa, dharma practitioner, however it's negated, so it's no dharma practitioner.
One way to fully translate this is: You are no dharma practitioner if you are attached to this life.
As for the meaning, there are many, the obvious one is that one is pleasant with one's life, thus is not achieving for any spiritual realizations. Another view Jetsun Drakpa Gyeltsen points out in his commentary is that anyone who takes for granted what is presented as how things are, by parents, school teachers, friends, politicians, and so on, they are not trying to figure out themselves how the world really works, thus they are not dharma practitioners.