A Trusted Aide

 is an unmarked quest in Fallout: New Vegas.

Quick walkthrough

 * Work for Caesar's Legion in order to gain access to Caesar's Legion safehouse.

Detailed walkthrough
Continue doing assignments given by Caesar's Legion members and earn their respect. Once you have reached the status of 'liked', you will be given the key to this safehouse by Lucius, leader of the Praetorian Guard. At this safe house there are multiple sets of legion faction armor and some weapons and the safehouse is made of two rooms connected by stairs.

Reaching a "liked" reputation can be accomplished multiple ways, one of the easiest may be to turn in 50 NCR dog tags to Severus or Aurelius of Phoenix. The player can turn in a smaller number and complete a few Legion quests also, which may require less time than gathering 50 dog tags, depending on how much of the world the player has explored already and factors such as their stealth or weapon quality, etc.