Here's an alternative way of tackling the problem:
Instead of trying to "fix it in post" why don't you truncate the description before the table needs to try and fit it into its columns? I did it like this:
<ng-container matColumnDef="description">
<th mat-header-cell *matHeaderCellDef> {{ 'Parts.description' | translate }} </th>
<td mat-cell *matCellDef="let element">
{{(element.description.length > 80) ? ((element.description).slice(0, 80) + '...') : element.description}}
</td>
</ng-container>
So I first check if the array is bigger than a certain length, if Yes then truncate and add '...' otherwise pass the value as is. This enables us to still benefit from the auto-spacing the table does :)