Grab the weapons nearby, including a Booshka grenade launcher. You can also activate the nearby Declassify Mission marker. (Sentry guns and laser fences guarding the area) Clear the first set of laser fences and turrets ahead. A grub hole will appear so dig in and throw a grenade in the middle to seal the hole and take out multiple enemies at once.
There will be more enemies in the front yard so take cover and take them out. There's a gnasher sentinel in the garage downstairs but be careful of the deployed turret and fence there. Once done, deploy the gnasher sentinel somewhere near the ramp or the front door of the house since enemies will emerge here later. Take out the mortar locust in the second level balcony in the mansion ahead. More enemies will appear later on, including a Reaver. Take cover and take it out. You can also grab the mortars on the balcony to take out the enemies faster.
Once it's dealt with, don't complete the section yet. Go to the mansion where the mortar-wielding locust is dealt with earlier and you'll find the COG skull behind some crates leading to a corridor. Go inside and you'll find the COG tag on a drawer to the right.