Since cilantro in guacamole mainly adds a fresh, citrusy flavor, you can substitute it with another herb that provides similar characteristics. In this case, parsley can be a suitable replacement for cilantro in your guacamole recipe. While parsley doesn't have the same distinct flavor as cilantro, it still offers a fresh, herbaceous note that complements the other ingredients in guacamole. Simply use the same amount of finely chopped fresh parsley as you would cilantro in the recipe. This substitution should maintain the overall flavor profile of the guacamole without drastically changing its taste.