There doesn’t appear to be a way to completely clear the arp cache of ESXi however you can remove specific entries one by one
Examples of command usage from VMWare host CLI:
esxcli network ip neighbor remove -a 10.1.1.250 -v 6
esxcli network ip neighbor remove -a 10.1.1.250 -v 4
-v is the IP version, ipv4 or ipv6