Severe setback (4,4)
I believe the answer is:
body blow
'severe setback' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for body blow that I've seen before include "A severe setback, like punch to solar plexus" , "Huge setback" , "Severe disappointment" , "Sickening reverse" , "Serious setback" .)