A press review is not dense (6)
I believe the answer is:
sparse
'not dense' is the definition.
(I've seen this before)
'a press review' is the wordplay.
'review' indicates anagramming the letters.
'a'+'press'='apress'
'apress' anagrammed gives 'SPARSE'.
'is' is the link.
(Other definitions for sparse that I've seen before include "Thinly scattered, not dense" , "Thinly distributed" , "Far from lavish" , "Rare" , "Meagre, thin on the ground" .)