Christmas attire: appear with this when half-cut (drunk) (5,3)
I believe the answer is:
paper hat
'christmas attire' is the definition.
(from inside crackers)
'appear with this when half-cut drunk' is the wordplay.
'this when half-cut' suggests halving the letters.
'drunk' indicates anagramming the letters.
'with' cut in half is 'th'.
'appear'+'th'='appearth'
'appearth' is an anagram of 'PAPER HAT'.
(Other definitions for paper hat that I've seen before include "Object from cracker" , "Wear for Christmas dinner" , "Content of a Christmas cracker" .)