Dinner for Dobbin is a phrase used to describe a meal of OATS and HAY, which are both common feed for horses. OATS is a four-letter word and HAY is a three-letter word, making them the solutions to the crossword puzzle. OATS are a type of cereal grain that is often used as animal feed, while HAY is a type of grass that is dried and used as fodder for animals. Together, these two items make up a nutritious meal for Dobbin, the horse.