Are you requesting from API v4 like required for clips?
Example request:
GET /kraken/clips/streamcorner/BraveWallabyMikeHogu HTTP/1.1
Accept: application/vnd.twitchtv.v4+json
Host: api.twitch.tv
Client-Id: d12jokwzby5m9e82gouqsjogd66inh
HTTP/1.1 200 OK
Date: Sat, 18 Feb 2017 13:40:33 GMT
Content-Type: application/json
Content-Length: 1525
Connection: keep-alive
Server: nginx
Access-Control-Allow-Headers: Accept, Authorization, Client-Id, Twitch-Api-Token, X-Forwarded-Proto, X-Requested-With, X-Csrf-Token, Content-Type
Access-Control-Allow-Methods: GET, POST, PUT, DELETE
Access-Control-Allow-Origin: *
Access-Control-Max-Age: 0
Twitch-Trace-Id: c900eff715f7a60b1cf8f3364c05601e
Front-End-Https: on
{"id":"streamcorner/BraveWallabyMikeHogu","url":"https://clips.twitch.tv/streamcorner/BraveWallabyMikeHogu?tt_medium=clips_api\u0026tt_content=url","embed_url":"https://clips.twitch.tv/embed?clip=streamcorner/BraveWallabyMikeHogu\u0026tt_medium=clips_api\u0026tt_content=embed","embed_html":"\u003ciframe src='https://clips.twitch.tv/embed?clip=streamcorner/BraveWallabyMikeHogu\u0026tt_medium=clips_api\u0026tt_content=embed' width='640' height='360' frameborder='0' scrolling='no' allowfullscreen='true'\u003e\u003c/iframe\u003e","broadcaster":{"id":"81300244","name":"streamcorner","display_name":"StreamCorner","channel_url":"https://www.twitch.tv/streamcorner","logo":"https://static-cdn.jtvnw.net/jtv_user_pictures/streamcorner-profile_image-a26d8edacc37c672-300x300.jpeg"},"curator":{"id":"17089325","name":"3v","display_name":"3v","channel_url":"https://www.twitch.tv/3v","logo":"https://static-cdn.jtvnw.net/jtv_user_pictures/3v-profile_image-aaa5f1b8946fa6b9-300x300.png"},"vod":{"id":"119593832","url":"https://www.twitch.tv/videos/119593832?t=14h45m17s"},"game":"Overwatch","title":"IS Striimicorner Assembly Winter 2017 @ Messukeskus, Helsinki, Finland","views":9,"duration":44,"created_at":"2017-02-05T17:26:53Z","thumbnails":{"medium":"https://clips-media-assets.twitch.tv/24428270176-offset-53074-44-preview-480x272.jpg","small":"https://clips-media-assets.twitch.tv/24428270176-offset-53074-44-preview-260x147.jpg","tiny":"https://clips-media-assets.twitch.tv/24428270176-offset-53074-44-preview-86x45.jpg"}}