This is a pun on the word "tier". The word "tear" has been replaced by the similar-sounding word "tier" because "tier" can refer to the way rows of seats are stacked up in a stadium and this joke is about a stadium. Alternatively, "tier" can refer to the relative level of something, as in "high tier". "High tier" is another way of saying "grandiose", and in the joke the architect's design is described as "grandiose".
When told his design for a stadium was too grandiose , the architect shed a tier .