How to apply a ltm policy to a virtual with icontrolRest on BigIp F5

"Missing name" sounds like the request didn't have the name of the policy.

Take a look at the JSON object you get when you query (GET) the virtual. e.g.,

 curl -sku admin: https:///mgmt/tm/ltm/virtual/vs\?\$select=policiesReference\&expandSubcollections=true

where vs is the virtual. An example output as below:

{
    "policiesReference": {
        "isSubcollection": true,
        "items": [
            {
                "fullPath": "/Common/TestPolicy",
                "generation": 20,
                "kind": "tm:ltm:virtual:policies:policiesstate",
                "name": "TestPolicy",
                "nameReference": {
                    "link": "https://localhost/mgmt/tm/ltm/policy/~Common~TestPolicy?ver=13.1.0.3"
                },
                "partition": "Common",
                "selfLink": "https://localhost/mgmt/tm/ltm/virtual/~Common~vs/policies/~Common~TestPolicy?ver=13.1.0.3"
            }
        ],
        "link": "https://localhost/mgmt/tm/ltm/virtual/~Common~vs/policies?ver=13.1.0.3"
    }
}

The

policiesReference

items

name

 curl -sku admin: https:///mgmt/tm/ltm/virtual/vs \
 -H "Content-type: application/json" -X PATCH \
 -d '{"policiesReference":{ "items":[ {"name":"TestPolicy"} ] } }'

Be careful with the closing ] and } as the data is heavily nested.