Sanction fraud on business (7)
I believe the answer is:
confirm
'sanction' is the definition.
(I know that confirm is a type of sanction)
'fraud on business' is the wordplay.
'fraud' becomes 'con' (con is a kind of fraud).
'on' says to put letters next to each other.
'business' becomes 'firm' (firm is a kind of business).
'con'+'firm'='CONFIRM'
(Other definitions for confirm that I've seen before include "Corroborate" , "Authenticate" , "Make (provisional arrangement) definite" , "Strengthen" , "Bishop may" .)