Again, from Le Carré's Tinker, Tailor, Soldier, Spy:
[George Smiley] had schooled himself to admit that in those last wretched months of Control's career, when disasters followed one another with heady speed, he had been guilty of seeing things out of proportion. And if the old professional Adam rebelled in him now and then and said: You know the place went bad, you know Jim Prideaux was betrayed - and what more eloquent testimony is there than a bullet, two bullets in the back? - Well, he had replied, suppose he did? And suppose he was right? 'It is sheer vanity to believe that one, fat, middle-aged spy is the only person capable of holding the world together,' he would tell himself. And other times: 'I never heard of anyone yet who left the Circus without some unfinished business.'
What is the author trying to convey here with the expression "professional Adam"? Wiktionary offers the figurative use of Adam to denote human frailty, but that doesn't appear to be a good fit here. ODO provides nothing along those lines.