tunnel - n. an underground passageway

smuggle - v. to illegally transport drugs or people

drug traffickers - n. criminals who transport illegal drugs

financier - n. a person or group that provides money for projects

light at the end of the tunnel - expression ​hope of success, happiness or help after a long period of difficulty; sign of improvement in a situation that has been bad for a long time

prefer - v. to like (someone or something) better than someone or something else

clay - n. heavy, sticky dirt or earth