No need to ask for pardon because of an excellent question. Hats off to you for investing in your future by looking to attend clinics to make yourself better. This is an excellent way to start as you prepare to become an NCAA official. Khackis and a nice collared shirt (golf shirt if warm weather) are perfect attire along with a decent pair of shoes. Business casual and you can't go wrong. A suit and tie would be overkill and shorts/sneakers wouldn't be appropriate. This is my opinion based on MY experience (about 10 clinics over the past 8 years). My advice is to take LOTS of notes. These clinics usually have well-experienced keynote speakers who enjoy imparting knowledge to help his/her fellow offiicals.