A think tank member is someone who is an expert in their field and provides advice and ideas to a group or organization. The two crossword solutions for this term are BRAIN and IDEAMAN, both of which refer to someone who is highly intelligent and creative. BRAIN is a 5 letter word that refers to the organ responsible for thought and reasoning, while IDEAMAN is a 7 letter word that refers to someone who is full of ideas and is able to come up with creative solutions. Both words are used to describe someone who is a member of a think tank.