The term 'Lamp Insert' refers to a device that is used to hold a light BULB in place. It is typically made of metal or plastic and is inserted into the socket of a lamp. The crossword solution for this term is 'BULB, ' which is a four-letter word. A BULB is an electrical device that produces light when electricity passes through it. It is usually made of glass and contains a filament, which is heated by the electricity and emits light.