Biblical twin brings account into work (5)
I believe the answer is:
jacob
'biblical twin' is the definition.
(I've seen this in another clue)
'account into work' is the wordplay.
'account' becomes 'ac' (abbreviation).
'into' indicates putting letters inside.
'work' becomes 'job' (job is a kind of work).
'ac' going inside 'job' is 'JACOB'.
'brings' is the link.
(Other definitions for jacob that I've seen before include "Name of patriarch" , "Twin of Esau" , "Hebrew patriarch" , "Bible character - old breed of sheep" , "Smooth character" .)