This is a multiplayer trophy.
You choose a faction when starting the multiplayer mode. Be sure to chose Firefly Faction in order to go for this trophy.
Complete 12 in-game weeks as a Firefly. 1 match is 1 day, so a little over 80 matches should make this pop.
After around 5 ingame weeks, clan vipes challenges start to appear. If you fail these, you're reset to day 1, week 1, losing quite a number of hours game in the process.
Below is the list of challenges,
Down enemies * (3 minimum)
Executions * (2 minimum)
Special Executions (2 minimum)
Revives (2 minimum)
Heal teammates (5 minimum)
Molotov Executions (2 minimum)
Downs with Bombs (2 minimum)
Gift Crafting Items * (2 minimum)
Mark Enemies * (7 minimum)
Downs with Melee (3 minimum)
Shiv Excutions (1 minimum)
Downs with 9mm Pistol (3 minimum)
Downs with Revolver (3 minimum)
Downs with Shorty (3 minimum)
Down Enemies with Hunting Rifle (3 mimimum)
Downs with Semi Auto Rifle (3 mimimum)
Downs with Burst Rifle (3 mimimum)
Downs with Bow (3 mimimum)
Downs from Long Range (2 mimimum)
Downs with Headshots (2 mimimum)
lostmantella9 recommends the 4 with the "*" next to them, plus downs with whatever weapon you're good with to survive these challenges.