Declare, formally, there’s cheat with company (7)
I believe the answer is:
confirm
'declare formally' is the definition.
(declare something officially)
'cheat with company' is the wordplay.
'cheat' becomes 'con' (conning is a kind of cheating).
'with' says to put letters next to each other.
'company' becomes 'firm' (firm can mean a company or business).
'con'+'firm'='CONFIRM'
'there's' acts as a link.
(Other definitions for confirm that I've seen before include "Ratify or verify" , "Establish the truth of" , "Bishop may" , "Strengthen" , "Authenticate" .)