I havent investigated this in a bit for Cluster mode but I believe the tools have gotten better. On GX it was a bit cumbersome:
https://kb.netapp.com/support/index?page=content&id=1011386&locale=en_US

network connections active show -instance -remote-address <client IP>

For this example, let's assume the client connection is coming from IP address 10.98.163.205:

ngsh::> network connections active show -instance -remote-address 10.98.163.205
Node: gxnode1
Connection Id: 46727253
Server: vs1
Virtual Interface Name: 10.98.163.30
Local IP address: 10.98.163.30
Local Port: 2049
Remote IP address: 10.98.163.205
Remote Port: 800
Protocol: TCP
Virtual Interface Id: 1025
Protocol Service: nfs
Least Recently Used: no

The value that is important above is the "Connection Id". In this case, the value is '46727253' on the controller 'gxnode1'. Take this value, convert it to hexadecimal, and then grab the lower-order 2-bytes (4-nibbles):
0d46727253 > hex > 0x0x2C90055

In this case, we're interested in the 0x0055. From the 'root' login on 'gxnode1' we execute the following command:

For NFSv3 statistics:
gxnode1# nperf 0 -p nfs3 -c 0x0055