Essentially a 'burn' about a burn (e.g. sunburn) that was mentioned in a particular episode of the ever-popular That 70's Show (see burn).
Jackie: Gee, I wish there was someone to help me put sunscreen on my body (hints Hyde).
Hyde: Good idea because sunburn could quickly lead to skin peeling.
Kelso: Aww man. That's a burn about a burn. That's like a second-degree burn!