If you light a fire under someone, you force them to act with more energy or to do something better. They need to improve their technical research and light a fire under their marketing team. It's hard to light a fire under people who don't think anything is wrong. Note: There is a story that some American farmers in the early part of the 20th century used to light fires under particularly stubborn mules that were refusing to move, in order to make them do so.