"clean as a whistle" meaning in English

{
  "etymology_text": ": → δείτε τις λέξεις clean, as, a και whistle",
  "forms": [
    {
      "form": "clean as a whistle"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "related": [
    {
      "word": "as"
    }
  ],
  "senses": [
    {
      "glosses": [
        "πεντακάθαρος"
      ],
      "id": "el-clean_as_a_whistle-en-phrase-OSub0Fxn"
    },
    {
      "glosses": [
        "δεν έχω εμπλακεί σε άνομη πράξη"
      ],
      "id": "el-clean_as_a_whistle-en-phrase-KleU-I4w"
    }
  ],
  "word": "clean as a whistle"
}

{
  "etymology_text": ": → δείτε τις λέξεις clean, as, a και whistle",
  "forms": [
    {
      "form": "clean as a whistle"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "related": [
    {
      "word": "as"
    }
  ],
  "senses": [
    {
      "glosses": [
        "πεντακάθαρος"
      ]
    },
    {
      "glosses": [
        "δεν έχω εμπλακεί σε άνομη πράξη"
      ]
    }
  ],
  "word": "clean as a whistle"
}