Authenticate scam by company (7)
I believe the answer is:
confirm
'authenticate' is the definition.
(I've seen this before)
'scam by company' is the wordplay.
'scam' becomes 'con' (both can mean a fraudulent scheme).
'by' means one lot of letters go next to another.
'company' becomes 'firm' (firm can mean a company or business).
'con'+'firm'='CONFIRM'
(Other definitions for confirm that I've seen before include "Substantiate" , "Establish the truth of" , "Authenticate" , "Make (provisional arrangement) definite" , "Provide supporting evidence, make definite" .)