Unoriginal confused daydream about theatre's closure (5-4)
I believe the answer is:
ready-made
'unoriginal' is the definition.
('ready-made' can be similar in meaning to 'unoriginal')
'confused daydream about theatre's closure' is the wordplay.
'confused' is an anagram indicator.
'about' indicates putting letters inside.
'closure' says to take the final letters (the letter which closes the word).
The last letter of 'theatre' is 'e'.
'daydream' is an anagram of 'radymade'.
'radymade' enclosing 'e' is 'READY-MADE'.
(Other definitions for ready-made that I've seen before include "Of clothes, off the peg, not specially created" , "Of clothes, mass-produced in standard sizes" , "Instantly available" , "Prefabricated" , "Of standard shape or size" .)