The term 'indulge in horseplay' can be summarized by two crossword solutions: SKYLARK (7 letters) and RASSLE (6 letters). Skylarking is a term used to describe mischievous or playful behavior, often involving running and shouting. Rassling is a form of physical play or sport, usually involving two people who try to gain control over each other by grappling and wrestling. Both activities are considered forms of horseplay, which is defined as rough, boisterous play or sport.