Horse Play: Clancy of the Outback series

In this book, Little Bill insists on turning Clancy into a country boy teaching him how to ride a horse. Little Bill turns up on a humungous bay horse and Clancy begins to wonder if he has bitten off more than he can chew. Clancy gets a tiny, mean-looking Shetland pony to learn to ride on. In the end, that pony and Clancy save the day!