Cake Blog reviewed jam (8)
I believe the answer is:
'jam' is the definition.
(I've seen this before)
'cake blog reviewed' is the wordplay.
'reviewed' is an anagram indicator (letters reviewed or revised).
'cakeblog' is an anagram of 'BLOCKAGE'.
(Other definitions for blockage that I've seen before include "Obstruction" , "jam" , "Clot" .)