Is a short account for a patriarch (5)
I believe the answer is:
isaac
'patriarch' is the definition.
(biblical patriarch)
'is a short account for a' is the wordplay.
'a short account' becomes 'ac' (abbreviation for account; 'short' suggests an abbreviation).
'for' says to put letters next to each other (I've seen this in other clues).
'ac' put after 'a' is 'aac'.
'is'+'aac'='ISAAC'
(Other definitions for isaac that I've seen before include "biblical figure" , "designated victim" , "Boy's name" , "Put away" , "Youth almost sacrificed" .)