MONICAH MWANGI WHEN lawyer Shadrack Wambui was growing up in one of Nairobi's slums, he vented his frustration at abusive police through boxing, cultivating discipline that helped him avoid confrontations that could have derailed his studies. Now the 29-year-old is turning to the sport again to help young people in poor Nairobi neighbourhoods, combining his passion for the sport with informal lessons on the law and legal clinics to resolve marital disputes. Wambui says he hopes his boxing sessions will help young people believe in themselves despite the challenges they face. "We want to use boxing to advance other causes…