The term 'ADHERENT' is often used to describe someone who follows a particular set of beliefs or practices. The two crossword solutions for this term are SUFF. (4 letters) and IST (3 letters). SUFF. stands for 'SUFFERER, ' which is someone who experiences pain or suffering, and IST stands for 'INSTRUMENTALIST, ' which is someone who uses an instrument to produce music. Both of these terms can be used to describe someone who is an ADHERENT to a certain set of beliefs or practices.