Final answer:
The irony in the phrase from Macbeth is that the lack of preparedness turns the will into a servant of defects, rather than being an agent of free and intentional action.
Step-by-step explanation:
The line “Being unprepared, Our will became the servant to defect, Which else should free have wrought”, from Macbeth, describes an ironic situation where the character recognizes that their lack of preparation has led to their will being subject to flaws, which otherwise would have been employed freely to achieve what they intended. This indicates how unpreparedness can enslave one's will to errors and faults, preventing the desired freedom of action. The irony lies in the unexpected outcome where the will, which is generally thought to be powerful and autonomous, becomes encumbered by the very defects it could have overcome with proper preparation.