"сястрою" meaning in Belarusian

{
  "forms": [
    {
      "form": "сястро́ю",
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "sjastróju",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "be",
        "2": "noun form",
        "head": "сястро́ю"
      },
      "expansion": "сястро́ю • (sjastróju)",
      "name": "head"
    }
  ],
  "lang": "Belarusian",
  "lang_code": "be",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Belarusian entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "form_of": [
        {
          "extra": "sjastrá",
          "word": "сястра́"
        }
      ],
      "glosses": [
        "instrumental singular of сястра́ (sjastrá)"
      ],
      "id": "en-сястрою-be-noun-lHDufzx3",
      "links": [
        [
          "сястра́",
          "сястра#Belarusian"
        ]
      ],
      "tags": [
        "form-of",
        "instrumental",
        "singular"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "[sʲaˈstroju]"
    }
  ],
  "word": "сястрою"
}

{
  "forms": [
    {
      "form": "сястро́ю",
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "sjastróju",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "be",
        "2": "noun form",
        "head": "сястро́ю"
      },
      "expansion": "сястро́ю • (sjastróju)",
      "name": "head"
    }
  ],
  "lang": "Belarusian",
  "lang_code": "be",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Belarusian entries with incorrect language header",
        "Belarusian non-lemma forms",
        "Belarusian noun forms",
        "Belarusian terms with IPA pronunciation",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "form_of": [
        {
          "extra": "sjastrá",
          "word": "сястра́"
        }
      ],
      "glosses": [
        "instrumental singular of сястра́ (sjastrá)"
      ],
      "links": [
        [
          "сястра́",
          "сястра#Belarusian"
        ]
      ],
      "tags": [
        "form-of",
        "instrumental",
        "singular"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "[sʲaˈstroju]"
    }
  ],
  "word": "сястрою"
}