The unnamed field agent is a character seen in Covert Front Episode 3.
At some earlier point of his life, he became a field agent for the Intelligence Agency General Headquarters. He was Kara's contact in Zurich. He was seen reading a newspaper, which he rolled up and hid a wallet and further instructions for Kara in the paper.
This man is seen wearing a long black coat and a bowler. Under the jacket, there are murky green pants and a brown suit. The man also seems to have a particularly big nose.
As a field agent, the man probably has some fighting skills, but the only skills we have seen are those of camouflage. He could pass himself as a commoner on a train station. However, the station was not very crowded and in fact, there was no-one to see the man in his disguise.