Average; par (4)
I believe the answer is:
norm
I believe this is a double definition.
'average' is the first definition.
(synonyms)
'par' is the second definition.
(I've seen this in another clue)
(Other definitions for norm that I've seen before include "Standard considered to be representative" , "Required or acceptable standard" , "Standard regarded as typical" , "Mean" , "expected thing" .)