Not accustomed to us appearing in the nude, perhaps (6)
I believe the answer is:
unused
'not accustomed to' is the definition.
(I've seen this before)
'us appearing in the nude perhaps' is the wordplay.
'appearing in' indicates putting letters inside.
'perhaps' is an anagram indicator.
'nude' anagrammed gives 'uned'.
'us' going inside 'uned' is 'UNUSED'.
(Other definitions for unused that I've seen before include "In mint condition" , "Extra" , "Surplus" , "'Fresh, new (6)'" , "idle" .)