The structure indicated is the iliopsoas muscle.
The iliopsoas muscle collectively refers to the distal ends of the psoas major and iliacus muscles which exit the pelvis to enter the anterior compartment of the thigh and insert onto the lesser trochanter of the femur.
The iliopsoas muscle is the strongest hip flexor.
Origin: Iliac fossa and vertebral bodies of T12 to L5
Insertion: Lesser trochanter of femur
Innervation: anterior rami of lumbar plexus (L2-L4)
Action: Hip flexion, lateral rotation of femur
Learn more about the muscles of the anterior compartment of the thigh in this tutorial.