Birdie plus one (3)
I believe the answer is:
par
'birdie plus one' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for par that I've seen before include "Rating of strokes required for hole (golf)" , "Normal golfing score" , "Expected golf hole score" , "Standard number of strokes for a golf hole" , "Standard number of strokes for a golf-hole" .)