Abraham's son's current appeal over bill (5)
I believe the answer is:
isaac
'abraham's son's' is the definition.
(I've seen this before)
'current appeal over bill' is the wordplay.
'current' becomes 'I' (physics symbol).
'appeal' becomes 'SA' (old-fashioned abbreviation for sex appeal).
'over' is a charade indicator (letters next to each other) (in a down clue, some letters go over others).
'bill' becomes 'ac' (short for account).
'i'+'sa'+'ac'='ISAAC'
(Other definitions for isaac that I've seen before include "Boy's name" , "-- Asimov, sci-fi author" , "Man's name" , "Youth almost sacrificed" , "Sir -- Newton, English scientist" .)