The term 'right-hand person' is a colloquialism used to describe someone who is an indispensable ASSISTANT or AIDE to another person. Two crossword solutions for this term are 'AIDE' (4 letters) and 'ASSISTANT' (9 letters). An AIDE is typically someone who provides direct support to a superior, while an ASSISTANT is someone who helps with administrative tasks. Both roles involve providing assistance to the right-hand person's superior.