A clenched fist is normally an aggressive gesture. With a tic-disorder, a clenched fist comes from an unwanted urge, and not a sign of aggression.
In ways, clenched fists tics can share similarities with tics like foot-stomping. They may appear aggressive or defensive, giving people the wrong perception.
This can lead to problems for children in school for example, not getting the help they need, or the wrong thing being addressed.
On top of that, pain from these tics can cause distress, and a combination of the above can lead to many issues.