The phrase "thinner icing" means that the layer of icing on a cake or dessert is not as thick as usual. It implies that less icing is used, resulting in a lighter and less sugary taste.
Sentences with «thinner icing»
I think they are living on thin ice with the amount of AC games. (gamercrash.com)
He compares the task to pulling newly formed sheets of thin ice off a pond in winter. (scientificamerican.com)
Tomorrow we might just go ahead and turn north before hitting the coast because we think we see thin ice in front of us. (dotearth.blogs.nytimes.com)