The word clogged up refers to something that is obstructed, blocked, or jammed. The antonyms for the word clogged up are open, unblocked, and clear. These words imply that something is not impeded or constrained but is free-flowing, accessible, and functioning properly. When a drain is open, it is not blocked, and water can easily flow through it. Similarly, when a person's mind is clear, they have no mental blockages or obstacles inhibiting their ability to think and reason. Thus, by using the opposite of the word clogged up, we can describe things that are free, open, and uninhibited.