Needs organising, being stupid (5)
I believe the answer is:
dense
'stupid' is the definition.
('dense' can be similar in meaning to 'stupid')
'needs organising' is the wordplay.
'organising' indicates anagramming the letters.
'needs' anagrammed gives 'DENSE'.
'being' acts as a link.
(Other definitions for dense that I've seen before include "Needs (anag) -- thick" , "Compressed - obtuse" , "Stupid, crowded together" , "Thick; stupid" , "Stupid; compacted" .)