DIY nut disorganised and messy (6)
I believe the answer is:
untidy
'messy' is the definition.
('untidy' can be a synonym of 'messy')
'diy nut disorganised' is the wordplay.
'disorganised' indicates an anagram.
'diy'+'nut'='diynut'
'diynut' anagrammed gives 'UNTIDY'.
'and' is the link.
(Other definitions for untidy that I've seen before include "Not neatly arranged" , "Messy, not neat" , "Scruffy" , "Careless, messy" , "Not inclined to be neat" .)