The term 'CELLO PART' can be broken down into three crossword solutions: VIOL (4 letters), KNEE (4 letters), and ENDPIN (6 letters). The VIOL is a stringed instrument that is similar to the cello, but slightly larger. It is held between the player's knees while playing. The KNEE is the joint between the upper and lower leg, which is used to support the cello while playing. The endpin is a metal spike at the bottom of the cello that is used to rest the instrument on the floor.