The phrase "a bit of heat" is an idiomatic expression that means to add some excitement, energy or passion to a situation. It can be used in various contexts such as adding spice to a conversation, livening up a party with music and dancing, or injecting enthusiasm into a project at work. The phrase implies the need for something more than just what is currently present - it suggests that there's a lack of excitement or intensity, and that some additional stimulus is needed to make things more interesting.