esquive is evasion in savate
in boxing evasion refers to slipping and to the B&W
in savate, we still do upper body and head evasion to punches, but also to kicks - this also involves ducking a spin kick
a leg esquive:
you are in left front stance, opponent round kicks your lead leg, you pull it back - you are now in right front stance
karate:
the karate retreating step in zenutsu dachi involves a lead hand block, pulling the leg far back is an esquive
kempo universal block - done with a retreating step, ergo an esquive
only savate names the leg evasion as a specific defence
displacement refers to a step - you would displace to attack, take a wide step with your left and kick with your right
to answer more directly, if you are in punch range the displacement step takes you out to kick range, so you would esquive evade the punches with slipping and weaving, and displace step to set up your first kick - that's why it works
eg - opponent attacks J, C, J
response - parry, slip, slip
on the second slip, your lead foot displaces, allowing the start of the spin kick