The phrase "addition to this" is a prepositional phrase that means something has been added or included as an extra element, apart from what was already mentioned. Full definition
In addition to in - class instruction, the school offers management - consulting engagements for students, as well as case competitions. (canadianbusiness.com)
This routine is under 12 minutes long, but it will be a great addition to mix in with other strength training routines. (lovingfit.com)
There are so many classic items that would make perfect additions to anyone's wardrobe. (adashofdetails.com)