Shouldn't this work?
code:
[root@mlnsrvmon01 scripts]# snmpwalk -v 3 -l authPriv -a SHA -A secret -u user -x AES -X secret1 10.21.1.10 -m /usr/share/snmp/mibs/NUTANIX-MIB.txt clusterName
NUTANIX-MIB::clusterName = No Such Object available on this agent at this OID