Crowdsourced review site (4)
I believe the answer is:
yelp
'crowdsourced review site' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for yelp that I've seen before include "Bark like a puppy" , "(Eg, dog's) short cry of alarm" , "old boast" , "bark sharply" , "Short sharp cry (of such as a dog)" .)