Returned to sign agreement and District Attorney's supplement (3-2)
I believe the answer is:
add-on
'supplement' is the definition.
(synonyms)
'returned to sign agreement and district attorney's' is the wordplay.
'returned' shows that the letters should be reversed in order.
'to sign agreement' becomes 'nod' (I've seen this before).
'and' is a charade indicator (letters next to each other).
'district attorney' becomes 'DA' (abbreviation).
'nod'+'da'='nodda'
'nodda' backwards is 'ADD-ON'.
(Other definitions for add-on that I've seen before include "Feature supplementing standard model" , "Extra unit, peripheral" , "Optional item as supplement or increment" , "Extra charge" , "Computer peripheral" .)