The term 'Swing Support' can be broken down into two crossword solutions: 'LIMB' and 'Tree'. LIMB is a four-letter word that refers to any of the projecting parts of a tree, such as branches or twigs. Tree is also a four-letter word that refers to a large plant with a trunk and branches made of woody tissue. Together, these two words refer to the support structure of a swing, which is typically a tree LIMB.