Pat chicken dry and season with salt and pepper.
Heat oil in a frypan on medium-high heat. Cook chicken for 3-5 minutes each side (depending on thickness), or until cooked through. Rest uncovered before thinly slicing.
While chicken cooks, thinly slice lettuce and dice tomato. Place in a bowl, crumble over feta and mix. Add in tzatziki and toss to cover.
Assemble wrap with chicken and salad. Serve any extra salad and chicken on the side.