The term 'register part' is a job description for someone who works at a cash register. This person is responsible for operating the register, handling customer transactions, and providing customer service. The crossword solutions for this term are 'TILL, ' which is a four-letter word. A TILL is a cash register or drawer where money is kept and transactions are recorded. It is an important part of the register part's job to ensure that the TILL is properly maintained and secure.