It's so ridiculous there's a theatre of it! (6)
I believe the answer is:
absurd
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for absurd that I've seen before include "Ridiculous, quite nonsensical" , "word to describe Beckett's theatre!" , "irrational" , "Incredible" , "Quite ridiculous, laughable" .)