Which Visa Type for Clinical Fellowship Training ?

A friend of mine is a Nepalese Citizen, MD in Pediatrics and is accepted for a clinical fellowship training in United Kingdom, Royal Manchester Children Hospital. His fellowship training is for a year (12 months) and is being sponsored by a UK not for profit organization (Kidney for Life) and International Society of Nephrology (ISN). The fellowship is some sort of training program for him, he will be working with UK doctors to get trained as well as looking after patients too. This typically is not a job, nor study but is some sort of professional development training.

So, we are wondering which visa type should he apply ? we looked into Visitor, Work/Academic, Tier 2/5 but nothing seems fitting for the purpose he is traveling. Does someone has some robust knowledge or someone who already had had applied such visa types, please Help !!