Birthday suit's state untidy, unfortunately (6)
I believe the answer is:
nudity
'birthday suit's' is the definition.
(thesaurus)
'untidy unfortunately' is the wordplay.
'unfortunately' is an anagram indicator (a bad or unfortunate spelling).
'untidy' with letters rearranged gives 'NUDITY'.
'state' is the link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for nudity that I've seen before include "Bareness" , "State of nakedness" , "element of naturism" , "The altogether" , "State of complete undress" .)