Untidy, eccentric in state of undress (6)
I believe the answer is:
nudity
'state of undress' is the definition.
(I've seen this before)
'untidy eccentric' is the wordplay.
'eccentric' is an anagram indicator.
'untidy' is an anagram of 'NUDITY'.
'in' acts as a link.
(Other definitions for nudity that I've seen before include "Unclothed state" , "that would horrify Mrs Grundy" , "State of being without clothes" , "Condition of having no clothes on" , "State of nature" .)