Last solution

Across: 1 Restrain; 5 Need; 9 Spot; 10 Advances; 11 Mount; 12 Private; 13 Stick-in-the-mud; 18 Disaster; 19 Pity; 20 Element; 21 Inert; 22 Side; 23 By-the-bye.

Down: 2 Exploit; 3 Titanic; 4 Independently; 6 Exclaim; 7 Distend; 8 Vanish; 13 Sadness; 14 Instead; 15 Kissed; 16 Expense; 17 Utterly.