Typical value, fraction reduced (3)
I believe the answer is:
par
'typical value' is the definition.
(average score in golf)
'fraction reduced' is the wordplay.
'fraction' becomes 'part'.
'reduced' means to remove the last letter.
'part' with its final letter taken off is 'PAR'.
(Other definitions for par that I've seen before include "A number of golfing" , "Average or normal score" , "Accepted level" , "Normal number of strokes for a hole at golf" , "Mean" .)