Needs new compact (5)
I believe the answer is:
dense
'compact' is the definition.
(similar in meaning)
'needs new' is the wordplay.
'new' indicates an anagram.
'needs' anagrammed gives 'DENSE'.
(Other definitions for dense that I've seen before include "Close - compact - stupid" , "Thick, compact or crowded" , "Stupid; compacted" , "Closely packed" , "Tightly packed - stupid" .)