The term 'SECURE (TO)' can be solved by the three-letter word 'TIE'. This word is used to describe the act of fastening or binding something with a rope, cord, or other material. It is also used to refer to a connection between two people or things, such as a relationship or bond. In terms of security, it can refer to making something safe and secure, such as tying down a load on a truck or securing a door with a lock.