A: "Sometimes big corporations, they have fixers on their payroll to prevent corporate espionage." A 'fixer' in this case is someone who works for the corporation in a spy like role to stop other companies from stealing ideas from the company he works for. B: ""Or clever detective from learning about said espionage". So again, the 'fixer' in this case is preventing a detective (either from the police or a private detective) from figuring out the spying that his/her company is doing on another company.