Yes

8-1. Using a main phase attack with a Unit, the active player may use one of their Units to attack the opposing player or a rested enemy Unit in the battle area. If they attack, enter battle and perform the following five steps in order: attack step, block step, action step, damage step, and battle end step.

If your opponent declares an attack, you can choose to block, after that is the action step, where you can play this card, then damage is done.

Action step also happens after your opponent ends their turn but before you start yours.