Age of Father Abraham (3)
I believe the answer is:
era
'age' is the definition.
(both can mean a long time)
'of father abraham' is the wordplay.
'of' indicates the answer is hidden within the clue.
'ERA' is hidden in the letters of 'father abraham'.
(Other definitions for era that I've seen before include "Characteristic period" , "8" , "day" , "Long period of history" , "Distinctive period of time" .)