"And you should protect my protection" meaning- you should make a fence for my protections the sages were commanded to make fences around the Torah-to place barriers around a mitzva from the Torah if it's something that they were commanded by way of prohibition, so they were commanded to fence off anything that may cause others to stumble in that prohibition so we learn from this that in regards to all the mitzvot the sages put fences up but there are also mitzvot from the Torah that within the mitzva which is a mitzva from the Torah itself, there are branches and clauses affiliated with that mitzva. 