Leverage is being in a position where you can utilize something to advance or conquer a goal or foe many times your current size. The most popular example is David and Goliath.
In a startup, or in any small team, one of the main posts of leverage is speed. A smaller and more agile foe is faster and can move more flexibly than a larger foe. The one step a Goliath takes can mean 100 small steps for the David.
What the smaller entity doesn't have is size. This can mean physical (in a Goliath scenario), financial, number of people, total knowledge or any other asset. In fact in the size category a small opponent has virtually nothing.
Another advantage a small opponent has is skill. This isn't any type of skill though - this is extreme proficiency in something that can take down a Goliath, practiced to the extreme degree. As Bruce Lee said, he doesn't fear the person that has practiced 10,000 kicks once, he fears the person that has practiced one kick 10,000 times.
The combination of skill and speed should take down size. There's also a need for courage though - in believing that this combination will indeed take down the Goliath.