The term 'UNITES FIRMLY' can be solved by the crossword solution 'CEMENTS', which is a seven-letter word. Cement is a material used in construction that binds other materials together and hardens to form a solid mass. It is made from a mixture of limestone, clay, and other materials that are heated and ground into a powder. Cement is often used to bind bricks, stones, and other building materials together, making them stronger and more durable.