Pen name of the American novelist and humorist Samuel Langhorne Clemens

Student changing into top from M&S makes promiscuous one horny5 Animal hair3 Liberal spreading often a good thing for soil5 English theatre director who founded the Liverpool Everyman Theatre and ran the RSC for 13 years10 Wild5 Shut, leaderless, small cafe sadly suffers blow to reputation9 Small biting insect commonly found near stagnant water4 Coffee variety7