Why is this the answer?

The answer is footstep because this riddle is a very smart puzzle that hides the answer inside the word itself. To solve it, you need to break the word "footstep" into two smaller words: "foot" and "step." First, let us look at the beginning of the riddle, which says "My second is performed by my first." The first part of the word is "foot" and the second part is "step." If you think about walking, your foot is what makes a step happen. Your foot is the thing doing the work, and the step is the action that your foot completes. So, the "step" (the second part) is definitely performed by the "foot" (the first part). Next, the riddle gives us a final clue: "it is thought a thief by the marks of my whole might be caught." The "whole" is the full word "footstep." When a person is running away or sneaking around, they might leave marks on the ground. These marks are called footprints, and they are left by a footstep. A detective or an officer might be able to follow the marks of a thief’s footsteps to figure out where they went, and that is how the thief could get caught. The single word "footstep" connects all the different parts of the riddle together in a clever and sneaky way. It is a brilliant example of how riddles can play wonderful tricks with simple words you use every day.