Chapter 6: Welcome to the CIA
This chapter is a series of three different types of training, one of which is fighting lessons. There are about three separate lessons, and you have to win each one while avoiding hits.
If you are playing on the "I rarely play games difficulty" it's quite easy to do without taking any hits at all. Just watch for the prompts (all of which will be joystick direction movements) and follow the movements.
The trophy will unlock after you complete the chapter, or, if you've finished the final fight and quit to main menu, it will unlock when you continue/load another chapter.