Worse than expected (5,3)
I believe the answer is:
below par
'worse than expected' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for below par that I've seen before include "Not in full health" , "Worse than expected" , "Not up to usual standard, like golfer" , "Worse than usual" , "Lower than the average, as in golf score ( 5, 3)" .)