It appears that the only feature that grants AC is the level 1 ability to add Wisdom to the Dex and a base of 10, there appear to be no other feature, trait or feat that increases this. So the only way a Adept can increase their AC is by acquiring magic items or increase stats.
You could instead take Brutal Defense at level 1, which grants proficiency in Light Armor and lets you use your Strength mod instead of your Dex mod when wearing light armor, allowing you to use magic armor and the like.
Of course, you could simply gain Medium or even Heavy armor proficiency and avoid the Adept options that require light or no armor.
But if you choose the Agile Defense option, then just like a 5e monk your only choice is to up your attributes and find magic items. Unless you wish to take armor proficiency feats (or multiclass) and wear armor. Again, avoiding options that require light or no armor.
Use a shortsword which Adepts are proficient in, or another weapon that has the parrying property. "When you are wielding a parrying weapon and you are not using a shield, once before your next turn you can gain an expertise die to your AC against a single melee attack made against you by a creature you can see. You cannot use this property while incapacitated, paralyzed, rattled, restrained, or stunned."
You can also use Patient Defense and spend one exertion to Dodge as a bonus action on your turn.
Some Adept archetypes also have features to improve defense:
Blade Dancer (PMG MOAR: I) - Wall of Steel at 11th level: While wielding a Fencer’s Arsenal weapon, when you use your reaction to perform a parry [..], you can do so without expending your reaction, up to a number of times equal to your proficiency bonus each round.
Tranquil Master (GPG#3) - Unassuming at 6th level: When hit by a melee attack, you can use your reaction and spend 2 exertion to add roll your martial arts die and add it to your AC for 1 round, including the triggering attack.
The Adept usually isn't a "stand and fight" combatant but one who usually isn't there when his enemies (if they are still standing) are able to hit back. Disengange and move away farther than the enemy can walk in a move usually prevents them from hitting you (at least if they got only melee attacks)