The term 'Guinea Pig's Pad' can be solved by the four-letter word 'CAGE'. A CAGE is a structure used to contain animals, such as guinea pigs, and provide them with a safe and comfortable environment. It is typically made of metal or plastic and has a door that can be opened and closed. The CAGE also provides protection from predators and other dangers. Guinea pigs need a large enough CAGE to move around in and have plenty of space to explore.