'Old Man River' as standard (3)
I believe the answer is:
par
'standard' is the definition.
(thesaurus)
'old man river' is the wordplay.
'old man' becomes 'pa' (both can mean father**).
'river' becomes 'r'.
'pa'+'r'='PAR'
'as' is the link.
(Other definitions for par that I've seen before include "Rap to get even" , "level footing" , "Standard number of strokes for a golf-hole" , "Rating of strokes required for hole (golf)" , "Target score (golf)" .)