This is a storyline achievement that cannot be missed while playing through the game.
At the end of Chapter 2, you'll reach this battle after going through an alley full of stormtroopers and other enemies. Then you'll get a quick cutscene of the Gunship coming to battle.
Take cover behind the barriers and when prompted, throw your lightsaber (LT + X) to hit the target. When it starts firing missiles your way, deflect them back to the gunship.
After doing this, you'll be prompted to mash the B button and force it to the left, causing damage.
Repeat the process til you're prompted to mash B again and force it to the right. Once the gunship crashes this time, it will be destroyed and the achievement will pop.