Impressive, but badly organised (9)
I believe the answer is:
grandiose
'impressive' is the definition.
('grandiose' can be similar in meaning to 'impressive')
'badly organised' is the wordplay.
'badly' indicates anagramming the letters.
'organised' with letters rearranged gives 'GRANDIOSE'.
'but' acts as a link.
(Other definitions for grandiose that I've seen before include "Ridiculously impressive or imposing" , "I grade son as affectedly splendid" , "Impressive, magnificent" , "Bombastic" , "Pretentiously magnificent" .)