Question

2. Do you have any idea        while his sister is playing with her little friends? (do)

当他妹妹正和小伙伴玩时，你知道Tom在做什么吗？

Answer 1

2. what Tom is doing整个从句可看成是idea的同位语从句，what在它引导的从句中充当宾语，说明idea的具体内容。