"special retainer" meaning in English

{
  "forms": [
    {
      "form": "special retainers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "special retainer (plural special retainers)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English 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"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Law",
          "orig": "en:Law",
          "parents": [
            "Justice",
            "Society",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "coordinate_terms": [
        {
          "word": "general retainer"
        }
      ],
      "glosses": [
        "A fee paid to counsel for work on a particular case."
      ],
      "id": "en-special_retainer-en-noun-g0m4bfPZ",
      "links": [
        [
          "law",
          "law#English"
        ],
        [
          "fee",
          "fee"
        ],
        [
          "counsel",
          "counsel"
        ],
        [
          "case",
          "case"
        ]
      ],
      "raw_glosses": [
        "(law) A fee paid to counsel for work on a particular case."
      ],
      "topics": [
        "law"
      ]
    }
  ],
  "word": "special retainer"
}

{
  "coordinate_terms": [
    {
      "word": "general retainer"
    }
  ],
  "forms": [
    {
      "form": "special retainers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "special retainer (plural special retainers)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Law"
      ],
      "glosses": [
        "A fee paid to counsel for work on a particular case."
      ],
      "links": [
        [
          "law",
          "law#English"
        ],
        [
          "fee",
          "fee"
        ],
        [
          "counsel",
          "counsel"
        ],
        [
          "case",
          "case"
        ]
      ],
      "raw_glosses": [
        "(law) A fee paid to counsel for work on a particular case."
      ],
      "topics": [
        "law"
      ]
    }
  ],
  "word": "special retainer"
}