Show as claret cup, erroneously (11)
I believe the answer is:
spectacular
'show' is the definition.
(spectacular is a kind of show)
'as claret cup erroneously' is the wordplay.
'erroneously' indicates anagramming the letters.
'as'+'claret'+'cup'='asclaretcup'
'asclaretcup' anagrammed gives 'SPECTACULAR'.
(Other definitions for spectacular that I've seen before include "Lavish production" , "Marked, very dramatic" , "Thrilling in effect" , "really striking" , "Very striking or dramatic" .)